# CO2 Solubility Experiment - Photos, Video.....Evidence!



## shalu (Jan 16, 2003)

unirdna said:


> If we continue the extrapolation (and I know I'm reaching now, but please bear with me), we calculate:
> 
> 450*1.6*1.6* = 1152ppm CO2.


Take a look at Roger Miller's chart:
http://aquabotanicwetthumb.infopop.cc/eve/ubb.x/a/tpc/f/8796060812/m/9686086835

at PH 5.59, CO2/KH = 88 approximately, that gives you 
CO2 = kh * 88 = 15 * 88 = 1320 ppm


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## windsurfer (Mar 8, 2005)

bravo !

-jd


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## lumpyfunk (Dec 22, 2004)

so your stating that the micro bubles are not possible, based upon the ability of CO2 to disolve in water?

I understand that water can hold a lot more CO2 than 30ppm, but then what are the "micro bubles" and is there a law (if henrys does not cover it) that states that this is an impossibility? 

I love the video response btw.

And I am no scientist, I just like understanding why.


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## lumpyfunk (Dec 22, 2004)

I thought I figured out the answers by reading CO2 revalations 2 but now I am more confused by what Tom said on page 4.


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## unirdna (Jan 22, 2004)

lumpyfunk said:


> so your stating that the micro bubles are not possible, based upon the ability of CO2 to disolve in water?
> 
> I understand that water can hold a lot more CO2 than 30ppm, but then what are the "micro bubles" and is there a law (if henrys does not cover it) that states that this is an impossibility?
> 
> ...


My data suggests that whatever CO2 is in those microbubbles is dissolving out quickly. What gas is left over, or what gas diffuses into those bubbles is not a question I set out to answer. 

The CO2 ppm was around 40 when I bubbled all that CO2 into my reactor. The reactor completely dissolved 30 more ppm (under not-so-turbulent conditions) into my tank in less than a couple minutes. If you will, a huge "bubble" of Carbon Dioxide was released into my reactor (you saw the video), and completely dissolved in less than two minutes. It was stated on pg 4 of that thread that the microbubbles were lasting 2-5 minutes in turbulent solution. How does a huge amount of gas dissolve more quickly than a small amount. This does not make sense. Why would the solution "allow" micro bubbles of CO2 to blow around the tank undissolved for lengthy periods of time? I contest that this couldn't happen.


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## jgc (Jul 6, 2005)

I will look at my hagen ladder diffuser tonight and post back on what the rate the co2 bubbles disolve. My wag is I am about 2 bubbles/second at the bottom, and 1 every 10 seconds at the top (near the top, the bubbles are moving so slowly that they end up touching, and smaller bubbles become larger ones - the bubbles that exit are about the same size as the initial ones)- with about 45 seconds of travel time.

Your experiment proved that co2 will disolve rapidly in turbulent conditions. Allowing bublles to float with the current (or in my case slowly rise up a ladder) will slow that a bit. From what I am seeing I suspect some micro bubles will be persistant for quite a few seconds - and a mister will be adding thousands of them (not sure they will combine like they do on a ladder or not).


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## BlueRam (Sep 21, 2004)

unirdna:

A better analysis would be preformed via the Henderson-Hasselbalch equation:

pH=pKa+log([A-]/[HA])

pKa bicrobonate system 6.36.

A link that contains too much science:
http://scifun.chem.wisc.edu/chemweek/CO2/CO2.html

"At room temperature, the solubility of carbon dioxide is about 90 cm3 of CO2 per 100 mL of water. "


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## unirdna (Jan 22, 2004)

jgc said:


> I will look at my hagen ladder diffuser tonight and post back on what the rate the co2 bubbles disolve.
> 
> From what I am seeing I suspect some micro bubles will be persistant for quite a few seconds - and a mister will be adding thousands of them (not sure they will combine like they do on a ladder or not).


I welcome your contribution, however I'm not seeing how the passive diffusion of large bubbles on a Hagen ladder can help to confirm or deny my findings. I've watched a hagen ladder. Bubbles are much smaller as they approach the top of the ladder. I would estimate they lose 90+% of their volume, and all without the need of turbulent flow. Please explain the purpose of your experiment for me.

As for the second part of your quote, you should be raising your own questions as to why some microbubbles would be persistant? Are they not all made of CO2? Why is some CO2 harder to dissolve than other CO2? Why would "most" of the CO2 immediately dissolve, and some not? How does this make any sense if we already know that CO2 is no where near the saturation point?

Here's what I'm NOT arguing against:
1. Bubbles being immediately released from the diffuser are mostly CO2

Here's what I am agruing:
2. In a fraction of a second all CO2 in those microbubbles dissolves into solution, and you are left with any "impurity gasses" that might have been in the original bubble, plus any (non-CO2) gasses in the tank that diffused into the bubble.

Here's my hypothesis:
3. Ever fill a tank up with fresh tap water? Did you see all the bubbles form on the walls? Where does this gas come from? It's in the solution. Oxygen and Nitrogen are the likely gasses, but that's not the point. The point is that these gasses are not CO2 (we know this by testing the pH), and that they ARE something other than CO2. And these gasses come out of solution when the water is saturated or supersaturated. A bubble, any bubble, provides a gas/liquid interaction (like the surface of your tank) that could allow any gas to diffuse in and out. I contest that along with whatever impurity is contained in the CO2 bubble, there is also gas (likely oxygen, since O2 becomes saturated due to photosynthesis) diffusing into that bubble (out of solution), while CO2 diffuses into solution (out of the bubble). What you are left with is small bubbles of Oxygen blowing around the tank.


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## unirdna (Jan 22, 2004)

BlueRam said:


> unirdna:
> 
> A better analysis would be preformed via the Henderson-Hasselbalch equation:
> 
> ...


Thank you BlueRam, I'll look into a more accurate calculation. Please feel free to contribute your calculation as well (using my pH KH data). But, I don't want to digress from my original point too far; CO2 dissolves very quickly and very easily in water, and 30 ppm doesn't even make a dent in CO2 solubility - concluding that any/all CO2 will want to quickly and easily dissolve into water regardless of the size of bubble it is in.


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## jgc (Jul 6, 2005)

My thought was this – diffusion is not instantaneous. I watch bubble diffuse for over a minute. This is in an area with some current. Small bubbles suspended in solution will have effectively no current. I suspect their diffusion rates as a relation to their surface area will be no greater than what I witness on my ladder if not slower.

I don’t know the terms, but the water in direct contact with the surface of the bubble will probably reach saturation fairly quickly – but that will have to be spread through the solution – and without current/turbulence, that will take time


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## Hypancistrus (Oct 28, 2004)

Nice experiment, but what I think we really need is an experiement with two identical planted tanks (preferably new), except that one has a CO2 reactor (like the Aqua Medic Reactor 1000), and one has a ceramic diffuser disc.

I don't think anyone doubts that CO2 levels in water aren't saturated at 30 ppm. If water is saturated with CO2, it's going to look like club soda!


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## unirdna (Jan 22, 2004)

jgc said:


> Small bubbles suspended in solution will have effectively no current. I suspect their diffusion rates as a relation to their surface area will be no greater than what I witness on my ladder if not slower.
> 
> I don’t know the terms, but the water in direct contact with the surface of the bubble will probably reach saturation fairly quickly – but that will have to be spread through the solution – and without current/turbulence, that will take time


I look forward to your findings. 

However, I do not agree that small bubbles suspended in solution have effectively no current. Just because a bubble doesn't have enough buoyancy to rise quickly does not mean it's not in current. The argument has been made that it is possible to blow tiny bubbles of CO2 around a tank using a powerhead. I hardly call these conditions "currentless". Additionally, tiny bubbles have to move very little to be out of any saturation zone they may have made. A "microbubble" needs to move only a "microdistance" to be out of any saturation zone it may have made. Finally, even if water is not "flowing" it is still moving. At the molecular level, water vibrates. This is what creates passive diffusion in the first place. Place a drop of food coloring in water. Doesn't it "bleed" around the water column?


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## unirdna (Jan 22, 2004)

Hypancistrus said:


> Nice experiment, but what I think we really need is an experiement with two identical planted tanks (preferably new), except that one has a CO2 reactor (like the Aqua Medic Reactor 1000), and one has a ceramic diffuser disc.


I agree this would be an interesting experiment, but I feel the need to once again say that I never once argued which method (reactor or diffuser) grows plants better/faster. 



Hypancistrus said:


> I don't think anyone doubts that CO2 levels in water aren't saturated at 30 ppm. If water is saturated with CO2, it's going to look like club soda!


It's not enough to know that CO2 levels are not saturated at 30ppm. One needs to know that CO2 levels are no where near saturation at 30ppm, so that they do not make the mistake of thinking that CO2 becomes more difficult to dissolve. 

As far as water is concerned it will dissolve CO2 virtually as easily at 30ppm as it will at 0ppm. This is key when someone makes the claim that "Once a high level builds up, then it becomes much more difficult for the CO2 mist to be dissolved."


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## rrguymon (Jul 10, 2005)

Nice experiment. I learned a lot. CO2 disolves much faster than I though.

I would say you are correct. While something might be promoting better growth with Tom's reactor or with diffusers and water current. You have convinced me it is not CO2 saturation at 30ppm causes the co2 bubbles to persist.


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## Wasserpest (Jun 12, 2003)

I always thought that what's collecting in the reactor after noon is not CO2, but O2. Why? The pH of the tank water doesn't change that much from mornings to evenings, so the CO2 level is about the same. So saying that higher CO2 concentration in the water keeps more CO2 from dissolving doesn't make sense IMO.

Basically I agree with you.

I think in the afternoon Toms micro bubbles (tm) are not CO2, but O2. It's O2 concentration that saturates in our tanks and makes plants pearl, reactors gargle, filters choke and venturi back loops spit out micro bubbles. 

Lots of little bubbles tell me O2 saturation is reached. That happens because plants photosynthesize like crazy. Meaning they grow quickly. Micro bubbles = fast growth. You decide which is the cause and which the result.

:fish:


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## shalu (Jan 16, 2003)

If those micro bubbles do not exist when the lights first turn on, but present late in the photoperiod, then I would have to agree, they are not likely CO2, but O2. Another way to verify this: some people leave CO2 on 24/7, so CO2 can be around 30ppm all day, do they see the same micro bubbles when the light first turn on(using Tom's CO2 diffusion method)?


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## Wasserpest (Jun 12, 2003)

Typically, in the mornings the reactors are quiet, and no bubbles are floating around in the tank. With 24/7 CO2 injection.


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## scolley (Apr 4, 2004)

Great thread Ted! roud: 

It had to be done. Glad someone did it. Too many major assumptions flying around about CO2. I look forward to all this being concluded, and this thread should be a big factor. Thanks.


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## SCMurphy (Oct 21, 2003)

Thanks Ted, It's nice to be validated.


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## lumpyfunk (Dec 22, 2004)

Does anyone know why Tom belives that the micro bubles are rich in co2 as he states in CO2 revelations #2


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## BSS (Sep 24, 2004)

I've been making some changes to my tank to try out the "revelation" and have been recording my observations. One thing I note in my tank is that my CO2 is *always* greater than 30 ppm. My KH=7.5-8. My high-end CO2, just before lights/CO2 on, is at or below 6.8 which has a CO2 ppm around 35ish. The low point, around lights out is 6.5 to 6.6, so ppm is in the 60-70 range. I typically note the bubbles building up throughout the day. Pearling has been better than before, but it's not knocking my socks off. Growth seems to be more compact and at a slightly faster rate...but am I just looking for that? One thing I note, is that later in the day, bubbles seem to be blasting out of the now-vertical spray bar. As the CO2 still appears to be mostly dissolving and resulting in very small bubbles trapped just below my protein slick  , I don't see how they would be getting sucked back into the filter to be blasted back via the spraybar. So, I've been thinking that it's mostly O2 (purely a guess though!) that is being sprayed around the tank.

FWIW,
Brian.


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## Robert H (Apr 3, 2003)

Assuming I can follow this, which I cant exactly, I still do not understand the relevance. You seem to be saying that C02 dissolves as soon as it hits the water regardless of the size of the bubble and regardless of what happens to the bubble. If that was the case we wouldn't need reactors or diffusors. All you would have to do is stick your tubing into the aquarium and let it bubble away. But I know, and many other people know from experience this is not the case. C02 bubbles disapate out of the water when they hit the water surface, even with no water movement.

I will relate an experience, not an "experiment" A few years ago I had a C02 system hooked up to an Aqua Medic reactor 500. This reactor pushes a bubble slowly down a coil inside a chamber where it comes into contact with water along the way and is expelled at the bottom. It took 1 bubble per second on this system to reach a pH 0f 6.9 with a KH of 8. When I switched over to an Eheim ceramic disk diffusor it took 3 bubbles per second to reach the same 6.9 pH and it was very difficult to hold it there and be stable. So which method do you think I prefer? When you mix the gas with water in a reactor it takes less gas to saturate the water and it is more stable than bubbling the gas into the water.


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## fishyface (Oct 7, 2004)

Robert H said:


> I will relate an experience, not an "experiment" A few years ago I had a C02 system hooked up to an Aqua Medic reactor 500. This reactor pushes a bubble slowly down a coil inside a chamber where it comes into contact with water along the way and is expelled at the bottom. It took 1 bubble per second on this system to reach a pH 0f 6.9 with a KH of 8. When I switched over to an Eheim ceramic disk diffusor it took 3 bubbles per second to reach the same 6.9 pH and it was very difficult to hold it there and be stable. So which method do you think I prefer? When you mix the gas with water in a reactor it takes less gas to saturate the water and it is more stable than bubbling the gas into the water.


i've had the same experience since i've changed over to a diffuser. seems as though my fish are alot more bothered bythe co2 bubbles in the water than when i was using the external reactor at the same pH. after trying the diffusion method for 2 weeks, looking at the pros and cons for both methods, i've returned back to the old fashioned way of the external reactor...for one reason, i use only a fraction of the gas that way.


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## unirdna (Jan 22, 2004)

Robert H said:


> Assuming I can follow this, which I cant exactly, I still do not understand the relevance.


The relevance is for me and the forum to better understand the physical and chemical properties of a molecule that is very important to the success of planted aquaria.




Robert H said:


> You seem to be saying that C02 dissolves as soon as it hits the water regardless of the size of the bubble and regardless of what happens to the bubble.


It sounds like you think I'm saying that any/all CO2, regardless of quantity will completely and instantaneously dissolve when it comes in contact with water. Of course, this is not what I am arguing. I'm saying that CO2 dissolves very quickly and easily; too much so for CO2 mist to NOT be dissolved when it is blown around an aqarium via a powerhead. 




Robert H said:


> But I know, and many other people know from experience this is not the case. C02 bubbles disapate out of the water when they hit the water surface, even with no water movement.


I'm not clear on what "even with no water movement" means exactly. Water movement is exactly what dissolves CO2 so quickly. Without any water movement, I think it's very possible for CO2 from a diffuser to reach the surface without dissolving _completely_. I've never used or seen an eheim diffuser in action, so I can't comment on its efficiency. But, if it was placed in an area with very little water current, not far from the surface, then yeah, I can envision conditions that would not completely dissolve all the CO2. 

An analogy: Ever make an instant drink such as koolaid? You started with sugar that needs to be dissolved into water. But, let's imagine that you only have sugar cubes (bubbles), not granular sugar (mist). Now imagine, that if any sugar were to hit the bottom of the container it would "escape". Of course, you would not want to waste your sugar, so you would first smash up all the cubes into granular suger (diffuser). This would increase the surface area to volume ratio, increasing the speed and ease of dissolving. Once, you had granular sugar (tiny bubbles of CO2), would you expect equal dissolve rates if you simply added it slowly, or if you added it slowly with the addition of stirring it? 

This is what a powerhead adds to the equation. Stirring the CO2 greatly speeds up diffusion. How many times faster? I don't know exactly, but many.

Would CO2 dissolve completely if the bubbles were too large, and rose quickly and passively through a short water column? Probably not. Would CO2 dissolve completely if it was added as a mist and stirred into a water column. Yes.




Robert H said:


> Aqua Medic reactor 500. This reactor pushes a bubble slowly down a coil inside a chamber where it comes into contact with water along the way and is expelled at the bottom. It took 1 bubble per second on this system to reach a pH 0f 6.9 with a KH of 8. When I switched over to an Eheim ceramic disk diffusor it took 3 bubbles per second to reach the same 6.9 pH and it was very difficult to hold it there and be stable.


As I mentioned before, I have no experience with Eheim ceramic diffusors, so I can not comment with confidence. More data would be need re: this diffusor and the conditions present in your tank when you used it.



Robert H said:


> So which method do you think I prefer? When you mix the gas with water in a reactor it takes less gas to saturate the water and it is more stable than bubbling the gas into the water.


I think you prefer the reactor, since, for you, it was more effecient and stable. But, to be fair, you were not duplicating the method that Tom Barr used. And once again, we see the word "saturate" pop back up when I've shown that any/all planted aquaria are never near the saturation point for CO2 (1500ppm). Misuse of jargon creates confusion.


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## Bert H (Dec 15, 2003)

Very interesting thread folks! Seeing is believing Ted, however, when I used to use the small power reactor on the inside of my tank, there was always a lot of gas (presumably CO2) which was swirling inside it and it didn't matter whether lights were on or off (it ran 24/7). Yet I see your film and the bubble disappears very fast?!

Judging from Robert's post, I am not the only scratching their heads here. But let's keep this up - a great learning experience.


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## albinooscar (Jan 25, 2005)

After reading all 3 threads this is what I get out of this.

1. The gas in the micro-bubbles is not CO2.

2. The reason for the increased plant growth has nothing to do with misting of the CO2 but rather the fact that there is more water movement in the aquarium providing a better and constant CO2 supply to the plants.

3. Why in the world would anyone want to see all these bubbles zooming around in the aquarium? I get the most enjoyment just after lights on when there are no bubbles and to have these micro-bubbles zooming around all day would drive me nuts!

My 2 cents,
Ron


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## unirdna (Jan 22, 2004)

Bert H said:


> Very interesting thread folks!  Seeing is believing Ted, however, when I used to use the small power reactor on the inside of my tank, there was always a lot of gas (presumably CO2) which was swirling inside it and it didn't matter whether lights were on or off (it ran 24/7). Yet I see your film and the bubble disappears very fast?!


Bert, I think you've hit the nail on the head re: confusion of CO2 solubility.

Reactors frequently collect other gasses besides CO2. Impurities in the CO2 line are one cause. The CO2 in your tank may be 99.x% pure, but that does not mean it gets to your tank at that same purity (line leaks, gas diffusion through tubing). Also, if you are using DIY CO2, you should expect a much much higher amount of impurities. Another cause (and I believe this is a big one) is gasses that come out of solution within the reactor.

It certainly does not help that the manufacturers of these reactors market them with photos of the reactors blasting bubbles everywhere. The consumer believes these bubbles to be CO2, but there is absolutely NO way CO2 is bouncing all over in those reactors without being dissolved. I don't think the manufactureres are intentially misleading people; I think that they themselves to not understand CO2 solubility. This lack understanding leads to "improvements" like sponges and bioballs; designed to keep "CO2" from escaping or to "chop up" that "hard-to-dissolve" CO2. Truth is, neither are needed, but neither are they detrimental (unless clogged with debris). You've seen my reactor, with no bioballs, dissolve 30 ppm into a 46 gallon tank (from 40ppm to 70ppm), under modest flow conditions, in less than 2 minutes. CO2 dissolves way more easily than most know.

Want proof? Try this.

When you notice gas building up in your reactor, tip your reactor to the side and let that gas out. Then restore your reactor to the original position. Notice what's happening now as the small bubbles of CO2 enter the reactor. The are dissolving completely and quickly. So why was that gas bubble (of "CO2") not dissolving as easily? Because it was not CO2. In time, your reactor will accumulate the gas again because of the afore mentioned reasons.

I can't tell you why you have gas in your reactor 24/7. My guess is that you at least have more at night, after a full day of photosynthesis, than you do in the morning, after a full night of respiration. But, every tank is different... Regardless, try emptying that gas out and try what I've mentioned. It may not prove what that gas is, but it surely will prove what it is not.


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## Robert H (Apr 3, 2003)

Well the Eheim diffusor is no different than the Amano diffusor or the Boyu diffusor, (the chinese knock off of Amano) It creates so called micro bubbles. The only difference is it is not made of glass.

I was talking about surface movement, agitation, splashing. When a bubble hits the water surface, it is still gassed out whether there is surface agitation or not, according to my experience. Tom's assertion is if the bubbles are moved around the tank by a current it is more effective than allowing the bubbles to rise to the surface. This may be true, but I do not think it is practical. If it is effective, it is because by moving the bubbles around it is in contact with water longer than if the bubble simply rises to the surface. He is also claiming that when the bubbles come into direct contact with the plants, the plants absorb the C02 faster. This may be true but again I think is not practical.

There has been a lot of documentation out there for years that states the longer a C02 bubble is in contact with water the more C02 is absorbed into the water. This is the principal behind the "Bell diffusor" which simply catches a bubble and holds it until it is absorbed. This is why power reactors have bio balls or other media in them which catch the bubbles and hold them while the water churns through them. Same principal is behind the membrane passive reactor. A current pushes the bubbles through a membrane that catches the bubbles while water passes through it.

Your experiment is putting a large amount of C02 into a very small container of water. Of course the pH is going to drop drastically. Do the same experiment with a much larger volume of water and see what happens.

Your assertions that the bubble coming directly out of the C02 line is not all C02 seems ridiculous to me. Put a tube in your mouth and blow into the water. The bubbles are pure carbon dioxide, not anything else other than bad breath!



> Reactors frequently collect other gasses besides CO2. Impurities in the CO2 line are one cause. The CO2 in your tank may be 99.x% pure, but that does not mean it gets to your tank at that same purity (line leaks, gas diffusion through tubing). Also, if you are using DIY CO2, you should expect a much much higher amount of impurities. Another cause (and I believe this is a big one) is gasses that come out of solution within the reactor.


What are you basing this on? If it is not C02, what else would it be? What impurities exactly are you talking about? Any impurities, (whatever this general, non specific term is supposed to mean in this case) would be miniscule and unmeasurable. You are feeding gas directly in the water. It bubbles in the water. The more you pump into a small place like a reactor, the more excess builds up, particularly if it is being pumped in faster than it can be dissovled into the water.


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## plantbrain (Dec 15, 2003)

unirdna said:


> I contested this point siting Scientific (Henry's Law), experimental, and practical evidence. Some agreed (and offered complimentary evidence), but others still chose to ignore the numbers, as if the planted tank hobby is absolved from the rules of the natural world.
> 
> I come offering hard data, photos, and a video. How you process this information is between you and your brain.
> 
> ...


'

Adding CO2 to a reactor(with bioballs etc) vs adding it to a tank are two quite different methods of adding CO2......... and 2 minutes is a long time concerning persistence...............

If you want to measure the persistence of a bubble , place a bubble in a counter current set up...............this will keep it from rising.
Watch and time the bubble with different dissolved CO2 levels.

You can do the same in a deep tank.

Many folks see the bubbles dissappear before they hit the surface...............
Well.............what were in those bubbles and not in the other ones that folks are suggesting stick around long after the CO2 was dissolved?

Why didn't the other "gases" persist in the reactor?

You cannot have it both ways...............

You'll need to reconcile that observation.

Regards, 
Tom Barr


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## plantbrain (Dec 15, 2003)

shalu said:


> If those micro bubbles do not exist when the lights first turn on, but present late in the photoperiod, then I would have to agree, they are not likely CO2, but O2. Another way to verify this: some people leave CO2 on 24/7, so CO2 can be around 30ppm all day, do they see the same micro bubbles when the light first turn on(using Tom's CO2 diffusion method)?


Okay, then why does the internal reactors which have no bioballs or other means of degassing acculmulate Gas in them later inj the day also?

The only gas being add to these is CO2..............not O2.
How is the O2 building up in there?

In an external reactor:
Why is the gas acculumated the day before so rapidly dissolved in the morning when flow is added again?

Even if the O2 levels are a little lower(a difference of 1.3-1.4), there should not be nearly the change in the gas levels we see in reactors, whereras the CO2 levels are over 10X different.

O2 is not very souble either.
CO2 is.

Add CO2 to the reactor in the morning, then try what builds up and time them.

I have an O2 gas system. I can( and have) added pure O2.

Regards, 
Tom Barr


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## plantbrain (Dec 15, 2003)

albinooscar said:


> 1. The gas in the micro-bubbles is not CO2.


Then what builds up in my internal reactor?
There are no bioballs etc, only water and CO2 are added and that is it.
Why would O2 degas there?
There is no logical reason for that to occur there.



> 2. The reason for the increased plant growth has nothing to do with misting of the CO2 but rather the fact that there is more water movement in the aquarium providing a better and constant CO2 supply to the plants.


The current was precisely the same in both cases I did this method on.
Only the placement of the CO2 mist into plant vs dissolved was changed.



> 3. Why in the world would anyone want to see all these bubbles zooming around in the aquarium? I get the most enjoyment just after lights on when there are no bubbles and to have these micro-bubbles zooming around all day would drive me nuts!
> 
> My 2 cents,
> Ron


Most folks like pearling.

Other observation and one we have all seen if you have done the hobby long enough, the plant near the outflow of a reactor..........

Do they pearl and grow the same as the plants furtherest away from the reactor?

The internal reactors I used cannot degas O2.
The externals might........but that can be tested(I'm doing this now)
Disc do not.

You need to use all 3 methods to see what is occurring here.

Regards, 
Tom Barr


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## shuks (Jul 10, 2005)

I did a little experament of my own, It's not that helpfull, but I'll report what I saw. In my 30 gallon tank, wich has no injected c02, c02 levels are about 3 ppm. I put a bubble ladder in the tank, and started injecting c02. At first the co2 bubbles would dissolve about 95% of their mass. The Next day, I mesured c02 levels about 20ppm. I knoticed that the bubbles wernt disolving as much as they did before. I would say that with a co2 level of 20 ppm, the bubbles would only dissolve about 75 % of it's mass. 

This is by no means a very good experament, but I just wanted to report what I knoticed. I can't be exactly sure about the % of the bubbles disolved incomparison to low co2 levels, and high ones. I am sure that the bubbles were noticibly smaller when the co2 levels in the tank were at 3ppm.


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## Wasserpest (Jun 12, 2003)

> Okay, then why does the internal reactors which have no bioballs or other means of degassing acculmulate Gas in them later inj the day also?


Because of O2 saturation.



> The only gas being add to these is CO2..............not O2.
> How is the O2 building up in there?


That's a good question. Some filters also accumulate this mysterious gas in the afternoons, even though there is no change in pH or CO2 injected amount. Still think it is O2, pearling out due to pressure gradients within the filter (or reactor).



> In an external reactor:
> Why is the gas acculumated the day before so rapidly dissolved in the morning when flow is added again?


Because what accumulates is O2. With O2 levels going below saturation after lights out, it can dissolve. When you add CO2 in the morning it rapidly dissolves as well (and does so all day).



> Even if the O2 levels are a little lower(a difference of 1.3-1.4), there should not be nearly the change in the gas levels we see in reactors, whereras the CO2 levels are over 10X different.


Huh?



> O2 is not very souble either.
> CO2 is.


But that's exactly the point Ted is trying to prove. You are suggesting CO2 has trouble dissolving and therefore can be easily moved around in the tank in micro bubble form.



> I have an O2 gas system. I can( and have) added pure O2.


So... what did you find?


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## eds (Feb 12, 2003)

I've got no idea what you guys are talking about.
I just can't believe how bored I must be at work here on a Friday afternoon that I just spent over a minute watching vid of a CO2 unit and in-line heater, with a the heater light playing the starring role and a hand making an occasional appearance! 
Please tell me I didn't miss the dramatic finish.
Did we get to see the other hand?
Did the light go off?
I'm going to go water my plants and surf ebay.


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## Hypancistrus (Oct 28, 2004)

I used to use the Aqua Medic Reactor 1000. I switched about a week ago to a diffuser disk in the tank.

I run airstones 24/7.

I had the gas buildup in the reactor when I ran CO2 into it.

Since using the diffuser disc and disconnecting the CO2 injection into the reactor, there is no gas buildup in the reactor whatsoever, at any time of the day or night.


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## scolley (Apr 4, 2004)

Hypancistrus said:


> I had the gas buildup in the reactor when I ran CO2 into it.
> 
> Since using the diffuser disc and disconnecting the CO2 injection into the reactor, there is no gas buildup in the reactor whatsoever, at any time of the day or night.


That indicates that the buildup in the reactor came from your CO2 tank. But it does not mean that the buildup was CO2, unless you want to assume that you have 100% pure CO2 in the tank.


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## bharada (Mar 5, 2004)

Of course what someone needs to do is take a sample of the build up gas and have it analyzed. A local LFS owner speculates that the gas could be mainly nitrogen...the product of CO2 tanks not being fully purged before filling.


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## unirdna (Jan 22, 2004)

Robert H said:


> Your experiment is putting a large amount of C02 into a very small container of water. Of course the pH is going to drop drastically. Do the same experiment with a much larger volume of water and see what happens.


You have missed the point of this experiement entirely. The first two paragraphs of my first post on this thread stated the purpose of my experiment. My arguement has nothing to do with pH. CO2 solubility is the topic.



unirdna said:


> Having heard enough speculation, I (and the forum) needed proof of the true potential of CO2 solubility. In this experiment, I've set out to get that proof.
> 
> It has been contested (on other threads) that 30ppm is a concentration where CO2 becomes more difficult to dissolve, allowing micro bubbles (of CO2) to be blown around an aquarium using a diffuser and powerhead.


In fact, I did do the experiment with a larger volume of water (my 46 gallon tank), and was able to drop the pH from 6.63 to 6.42 in less than 2 minute....though I fail to see the point of debating pH swings.



Robert H said:


> Your assertions that the bubble coming directly out of the C02 line is not all C02 seems ridiculous to me. Put a tube in your mouth and blow into the water. The bubbles are pure carbon dioxide, not anything else other than bad breath!


Why? Do you know all there is to know about the purity of pressurized CO2 sources? I get mine from a local welding store. I don't know their procedures or sources.

And as for human respiration, it is about 3% CO2 (at rest), 5 times less than the 15% Oxygen you exhale. As a freediver, I would love it if you were right, it would increase my breath hold time significantly. 



Robert H said:


> What are you basing this on? If it is not C02, what else would it be? What impurities exactly are you talking about? Any impurities, (whatever this general, non specific term is supposed to mean in this case) would be miniscule and unmeasurable. You are feeding gas directly in the water. It bubbles in the water. The more you pump into a small place like a reactor, the more excess builds up, particularly if it is being pumped in faster than it can be dissovled into the water.


By impurities, I mean any non-CO2 gas - sorry for the confusion. And again, how do you know they would be miniscule and unmeasurable? Nevertheless, you don't need to even know if such impurities exist (I'm starting to regret such speculation) to know that the gas can NOT be CO2. I never set out to prove what that gas is. I set out to show that CO2 was so very soluble in water that it would never "collect" or "persist" in any location of moving water. I belive I've done this, thoroughly. You talk about gasses like they are all the same. CO2, O2, N2.... "the more you pump into a small place like a reactor, the more excess builds up". But what if water can absorb 150 times more CO2 than O2. Well, if you bubble CO2 and O2 equally, would the ratio or non-dissolved gas still be the same??? As for the last part of this quotation: I'm feeling like a broken record when I once again draw your attention to my reactor video. I showed how a simple reactor, with no bioballs and moderate flow easily dissolved enough CO2 to raise the ppm in my 46g tank from 40-70 - in 2 minutes. Do you need to dissolve CO2 faster than that?


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## Wasserpest (Jun 12, 2003)

Hypancistrus said:


> I had the gas buildup in the reactor when I ran CO2 into it.
> 
> Since using the diffuser disc and disconnecting the CO2 injection into the reactor, there is no gas buildup in the reactor whatsoever, at any time of the day or night.


I suspect that the CO2 bubbles are being changed to O2, kinda like one gas attracting another. As a CO2 bubble is swirling around, CO2 diffuses into the water, but at the same rate O2 is moving into the gas bubble, replacing the CO2. When you don't use CO2, no bubbles, no O2 buildup.

I have and some of you might have experienced this: bubbling CO2 into canister filter airlocks (some, most of) them. Why? Again, it's not the CO2 which quickly dissolves. It's the O2 that makes them gargle.

I don't buy the N2 impurities, although it is possible.

Here is why... simple experiment. Use a DIY CO2 powered reactor. Mornings it will be pretty much empty, with the CO2 bubbles dissolving immediately. In the afternoons the BUBBLE builds up. Now do this: purge the bubble, so the reactor is empty. Squeeze your CO2 soda bottle so a CO2 bubble with the size of the previous bubble will be in the reactor. Watch it. It will dissolve very quickly.

What's wrong with this observation? It clearly proves to me that we are not dealing with CO2 buildup in the reactor.

Bill is right. Someone needs to analyze a bit of reactor burp. A little more sophisticated than holding a candle in it. :fish:


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## shalu (Jan 16, 2003)

Here is my observation of buildup in my reactor. Remember my CO2 is only ON with lights more or less. In the morning before the lights on, the buildup is still there, but is a few inches less than in the afternoon. It tells me that much of the buildup is not easily dissolved in water even after a whole night. My bet is mostly O2, well could be N2/Air as well.


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## unirdna (Jan 22, 2004)

Wasserpest said:


> Bill is right. Someone needs to analyze a bit of reactor burp. A little more sophisticated than holding a candle in it. :fish:


This is definitely high on my to-do list. I'm sure my place of employment has a gas analyzer somewhere. Time to start dropping emails and asking for favors. I intend to collect the gas by fixing a syringe to the purge valve on my reactor. The reactor has about 1 inch of air in it during the late evening. I'll make every effort to use a syringe that is impermeable to all the gasses relevant to our discussion.


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## Marc (Oct 13, 2004)

Robert H said:


> I will relate an experience, not an "experiment" A few years ago I had a C02 system hooked up to an Aqua Medic reactor 500. This reactor pushes a bubble slowly down a coil inside a chamber where it comes into contact with water along the way and is expelled at the bottom. It took 1 bubble per second on this system to reach a pH 0f 6.9 with a KH of 8. When I switched over to an Eheim ceramic disk diffusor it took 3 bubbles per second to reach the same 6.9 pH and it was very difficult to hold it there and be stable. So which method do you think I prefer? When you mix the gas with water in a reactor it takes less gas to saturate the water and it is more stable than bubbling the gas into the water.


I would like to clarify that the tubing size of an Eheim Ceramic Diffuser is smaller in diameter compared to the normal size tubing we are all familiar with.
So if you were looking into the Eheim diffuser to count the bubble rate, that would explain why you were seeing 3bps vs 1bps with the AM 500 reactor.

Also if you were using the check valve that came with the Eheim unit, that's probably why you were having a hard time keeping the rate stable. The check valves are junk IMO.


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## unirdna (Jan 22, 2004)

plantbrain said:


> Okay, then why does the internal reactors which have no bioballs or other means of degassing acculmulate Gas in them later inj the day also? The only gas being add to these is CO2..............not O2.
> How is the O2 building up in there?


Tom, you are approaching this question at an angle that is not logical.

In the video I posted, I've shown that I can dissolve enough CO2 in less than 2 minutes to raise the pH in my 46g tank from 40ppm to 70ppm. In two minutes! The solution was clearly no where near saturation to be able to dissolve that huge mass of CO2 so quickly and easily.

So when you see gas build up in a reactor, you should NOT be asking, "why does the CO2 in my tanks get to ignore well known solubility constants?". You should be asking,"since I know that gas can NOT be CO2 because of how easily and quickly CO2 dissolves, what other gas(ses) could that be and by what means did it (they) get in my reactor?"

Laws and constants are not "flexible". You know this. So why do you continue to argue that they are. Examine my data. Examine Henry's law. Examine the well-establish solubility curve of CO2. Repeat my experiment. See for yourself how quickly and easily CO2 dissolves. Then ask yourself, which is the most logical conclusion. Stubborn CO2 or some other gas?


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## albinooscar (Jan 25, 2005)

plantbrain said:


> Most folks like pearling.
> 
> Other observation and one we have all seen if you have done the hobby long enough, the plant near the outflow of a reactor..........
> 
> ...


I'm not talking about the pearling. I'm talking about the bubbles you are introducing with your "mister".

I seem to have all my plants pearling equally. roud: 

I don't think all 3 methods need to be done. I think analyzing the gas that is building up is the key to this whole debate.

Edit: I forgot to add that the water flow might me the same but when you add the bubbles the water flow becomes more turbulent which mixes it all more. Don't you think?

Ron


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## rrguymon (Jul 10, 2005)

plantbrain said:


> Okay, then why does the internal reactors which have no bioballs or other means of degassing acculmulate Gas in them later inj the day also?
> 
> The only gas being add to these is CO2..............not O2.
> How is the O2 building up in there?
> ...


I use an internal reactor similar to the DIY on the Tom Barr web page. I do get a build up of gas after the lights have been going awhile. I think it is O2. The plants start to pearl and release bubbles into the water and the pump on the internal reactor picks them up on the intake side and pushes them into the tube and the gas builds up in the tube.

The same thing happens with my canister filter in the afternoons. It picks up a lot of the o2 bubbles the plants release and they pass through the filter and spew out the spay bar ever so often. It never does this in the morning only late in the day after the lights have been on a long time.


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## lumpyfunk (Dec 22, 2004)

BFO I dont know why this took me so long to think of but it logically is not c02 that builds up in the reactor in the day, if it was co2 it would build up overnight in 24/7 setups


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## Rex Grigg (Dec 10, 2002)

lumpyfunk said:


> BFO I dont know why this took me so long to think of but it logically is not c02 that builds up in the reactor in the day, if it was co2 it would build up overnight in 24/7 setups



Simple, sweet and true.

If it were CO2 then the reactor should be full at night since the plants are not using any CO2.

If I get my tanks pearling heavily then I get a build up of gas in my canister filter. Simple deduction leads one to think that this is O2.


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## Robert H (Apr 3, 2003)

> You have missed the point of this experiement entirely. The first two paragraphs of my first post on this thread stated the purpose of my experiment. My arguement has nothing to do with pH. CO2 solubility is the topic.


But that is how you measure how much C02 is in your water! By how much the pH goes down! If you are not concerned with pH, then why did you mention the pH and KH? How do you know how much ppm of dissolved C02 you have if you don't measure the pH?

But you are right, I am probably missing something in this conversation, I said I was having a hard time following it. I mean no dis respect to your scientific genius, but this whole thing seems more pointless to me than Toms rant.



> I would like to clarify that the tubing size of an Eheim Ceramic Diffuser is smaller in diameter compared to the normal size tubing we are all familiar with.


No, sorry. I ran an external bubblecounter because the bubblecounter on the Eheim is useless, and I used 1/8 tubing just like I did with the reactor.


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## unirdna (Jan 22, 2004)

Understanding Laws that govern gas exchange

---------------------------------------------------------------

...all the confusion is due to folks not understanding how partial pressure governs gasses.

When you do not see a bubble of CO2 completely disappear, you assume that all the CO2 has not dissolved. This is wrong.

When your tank becomes saturated with O2 (at 10-12 ppm) because of photosynthesis, the O2 wants to escape the water. The O2 concentration in the water is higher than the equilibrium with the atmosphere, so it wants to escape back to the atmosphere.

But, lets think about this more critically. Henry's Law States "When a gas is in contact with the surface of a liquid, the amount of the gas which will go into solution is proportional to the partial pressure of that gas." The atmosphere is about 20% O2. Henry's Law says that when O2 is at 10ppm in water, any more O2 that is dissolved (given off by plants - photosynthesis) will want to escape to an atmosphere that already contains 20% O2.

Our bubbles of CO2 are almost pure CO2 (the debate goes on). The point is that there is little to no O2 in those bubbles when they first enter the water. So, the parital pressure of O2 in even lower in those bubbles than in the atmosphere. O2 not only will diffuse into those CO2 bubbles (while CO2 diffuses into the water), it actually prefers it!

So as O2 goes in and CO2 comes out, all the hobbiest sees is a stubborn bubble, refusing to dissolve.


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## jbaker6953 (Sep 18, 2005)

I thought of a good way to tell if these bubbles are CO2 once and for all. Just find some way to transfer some of the gas from these bubbles to a test tube containing a strong solution of CaOH (calcium hydroxide - kalkwasser). Shake it up. If it turns white, the gas is CO2 (forming calcium carbonate), if it doesn't, it isn't. End of story.


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## jbaker6953 (Sep 18, 2005)

I should add that collecting the air from the reactor won't work since it will have CO2 in it. One could shut off the CO2 supply and wait for a while before collecting from the reactor, but I think the best way would be an inverted beaker or something placed to collect the microbubbles for some time. Even that would collect some CO2 since the partial pressure of CO2 in the water would exceed that of the collected gas and cause some to diffuse into it. However, conducting the CaOH experiment twice with equal volumes of collected gas, and pure CO2, should make it easy to interpret the result.


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## Georgiadawgger (Apr 23, 2004)

This is a great thread! Nice work to all who have been trying to figure all of this out. 

My personal 2 cents:

I recently modified my external reactor from a top-down flow from my eheim input to a top-side flow which creates a vortex type swirl inside the reactor. The reactor was about 15 inches long. I noticed that the bioballs were necessary for my new design and the reactor had to be placed at a 20 degree angle...otherwise it was like a tornado inside of micro co2 bubbles and they were being shot out of the tube into the tank without being dissolved. 

This summer after my move to a bigger tank I was always puzzled why there was so much gas buildup inside the reactor when I came home (about 2-3 inches of gas) and thought it was O2 from supersaturation...then Tom's previous threads had me thinking it was CO2 that wasn't being efficiently dissolved. The wierd thing was my pH wasn't really dropping so my first deduction was it was o2 or some other gas other than co2. 

I was running my regulator on a timer where it would click on about 9 am and my lights on at 10 am...solenoid off at 7 pm...lights off at 8 pm. Not much change in co2, except my bubble count was obnoxiously high to keep a steady level. I was having to get a refill every 3 months or so. 

Then I switched to 24/7 with the same design (15 inches) and same bubble count. I come home and my pH is at the bright yellow reading on my pH kit and there was a 4-5 inch gas pocket in my reactor! The fish and shrimp were fine, but there was pearling like I haven't seen before and there were tons of micro bubbles coming out of the reactor...so then I thought about what Tom was mentioning about diffusion disks and a co2 mist. (pH dropped from 6.6 to less than 6)

Then I decided, there must be a way to minimize gas flow and make the reactor even more efficient and hold a low pH...I extended my reactor by another foot...so the reactor itself is a vortex reactor (top-side-downward flow from filter input) and its about 2.5 feet long (takes up a ton of room under the cabinet)...but my bubble count on my aquamedic bubble counter (I know its arbitrary) goes from about 3 bubbles PER second (a steady stream) to 1 bubble EVERY 3-4 seconds (this was a major PITA holding a watch and counting bubbles next to my analog watch). What I've noticed is there is very efficient dissolution of the gas and my pH is holding steady at 6.4 (about 50 ppm). This is running 24/7 and there is a steady level of gas inside the reactor regardless of night/day cycles. I've also noticed there is about a 1 inch pocket of gas at all times inside the reactor and no (visible or noticable) fluctuation in co2 concentration. 

Basically I've taken all the discussion and modified my external reactor into a monster that should make my cyclinder last at least twice as long and keep the plants happy.


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## jbaker6953 (Sep 18, 2005)

*Calculating pH/KH/CO2*

For anyone interested, it's ugly, but I have a calculator I wrote some years ago that does all the pH/KH math for you. It is a little different than Chuck Gadd's calculator since it can solve for any unknown (pH, KH, CO2). Check it out: http://www.bakerweb.biz/fish/co2calculator.html


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## Robert H (Apr 3, 2003)

> Our bubbles of CO2 are almost pure CO2 (the debate goes on). The point is that there is little to no O2 in those bubbles when they first enter the water. So, the parital pressure of O2 in even lower in those bubbles than in the atmosphere. O2 not only will diffuse into those CO2 bubbles (while CO2 diffuses into the water), it actually prefers it!


I can't argue this because I have no idea if it is true or not, or how it relates to me as a hobbyist. What is the bottom line of everything you have put forth? How does it relate to me as a hobbyist and impact me as a hobbyist? Why should I care if 02 diffuses the C02 bubble or not?

I uderstand you took a pH KH reading of your tank, took water out of the tank and put it in a much smaller container and then injected a large amount of C02 into that container. Am I correct so far? After that you lost me.

Please tell me again what the basic conclusions were from your experiment and in a very basic way explain how you reached those conclusions, and why it is important.



> So as O2 goes in and CO2 comes out, all the hobbiest sees is a stubborn bubble, refusing to dissolve.


I do not see stubborn bubbles, ever. I see bubbles that rise up to the water surface and disappear within seconds.


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## Bert H (Dec 15, 2003)

Dawgger,

Are you saying you made a longer reactor, are using a lower bubble rate and are running it 24/7 AND now have higher CO2 than before when you had a much higher gas flow rate and solenoid control? You think it is due to the reactor size? 

The only tank I have on solenoid control is the one I have this constant battle with to maintain a good 30+ppm CO2 on. The other tanks which run 24/7 have good CO2 levels. I am about to give up on the solenoid on/off.

I too have bubbles spewing out of my filter late in the photoperiod. I always assumed these were O2 due to the fact that on all tanks it only happens late in the day.


> I've also noticed there is about a 1 inch pocket of gas at all times inside the reactor and no (visible or noticable) fluctuation in co2 concentration


 According to what Ted is saying, this shouldn't be happening??!! Or at least, that it isn't CO2.


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## jbaker6953 (Sep 18, 2005)

Robert H said:


> I can't argue this because I have no idea if it is true or not, or how it relates to me as a hobbyist. What is the bottom line of everything you have put forth? How does it relate to me as a hobbyist and impact me as a hobbyist? Why should I care if 02 diffuses the C02 bubble or not?


The point is that Tom Barr has offered an observation that placing a CO2 diffuser into a strong water current to create a tank full of small bubbles increases plant growth and pearling over the same amount of CO2 being injected through a reactor. Tom theorized that this was because the bubbles were CO2 and when they adhered to the plants they were making CO2 more available to the plants. He observed that in the morning, at lights on, the bubbles weren't persisting long enough to travel all around the tank, but later in the day they did. Tom's reasoning was that as the CO2 concentration in the water column reached 30 mg/L, the CO2 had a more difficult time dissolving, thus explaining the persistence of the bubbles.

I argued that it is extremely unlikely that these persistent micro-bubbles actually contain any CO2 at all and that the persistence of the bubbles could be explained by increasing O2 saturation causing O2 diffusion into the CO2 bubbles.

This matters practically if you care about why Tom has seen increased pearling and better plant growth when placing a diffuser disk near a strong water current. If you don't care why things happen, and only care that they happen, then this is probably not going to be of any interest to you.



Robert H said:


> I do not see stubborn bubbles, ever. I see bubbles that rise up to the water surface and disappear within seconds.


That's probably because you are not plaing your CO2 diffuser into an area of strong current like we are speaking of.

The point of this experiment was to confirm or deny the theory that CO2 becomes difficult to dissolve above 30 mg/L.


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## unirdna (Jan 22, 2004)

Robert H said:


> What is the bottom line of everything you have put forth? How does it relate to me as a hobbyist and impact me as a hobbyist? Why should I care if 02 diffuses the C02 bubble or not?


Robert, I don't know if you were following the other recent "CO2" threads. In the thread titled "CO2 revelations part 2#", Tom Barr stated,

"Once a high level [of CO2] builds up, then it becomes much more difficult for the CO2 mist to be dissolved. Chemically: it is more difficult to dissolve a substance against an increasingly larger concentrational gradient."

His post was immediately followed with acceptance (with the exception of jbaker's post, which was a "ninja" post to my own). My experience with the hobby, as well as my occupational and formal education contradicted what Tom Barr stated. THIS is why I posted. Not for ego, but because I saw many folks, eager to learn more about the hobby, being misled by speculative (and more importantly, flat-out wrong) conclusions. Tom may have been right in the past re: other aspects of the hobby, but he was quite wrong this time. I knew that contradicting him would bring opposition from his followers. Some blind. Some inflammatory. Some honest. I knew it would start as an uphill battle, but I also knew that eventually, the evidence would speak for itself. If I would have overheard the conversation at a local pub, I wouldn't have felt the need to correct (actually, that would be quite rude), but this forum is a massive hub for information. NOT posting, was out of the question.

[Please tolerate a bit of "soap-boxing" for a moment]

A lot of research has been done to get us (the hobby) to where it is today. Some scientific, some anecdotal. I (and everyone else) have drawn upon much of that research to improve our success. Do you think we should stop now? Have we learned enough? That is a question I can't answer for you, nor do I want to. But, if you don't mind me "asking" a rhetorical question, why are you reading threads on this forum if you don't want to learn? I can't understand your position of indifference. As a hobbiest and buisness man, I would think you would want to know all you can.

[climbs down from the soapbox, thanks for your patience]





Robert H said:


> I uderstand you took a pH KH reading of your tank, took water out of the tank and put it in a much smaller container and then injected a large amount of C02 into that container. Am I correct so far? After that you lost me.


The point of this was simply to show to true solubility of CO2 in water. Tom Barr concluded that 30ppm was near saturation for CO2. This incorrect conclusion created many more incorrect conclusions. On the "CO2 revelations part 2#" thread, I attached a graph of the known solubility curve [of CO2 in water]. Apparently, this data was too imperical for some (including Barr) to understand, so rather than sack Tom's thread, I decided to start my own to SHOW this. And that is exactly what I did. Simply bubbling CO2 into water, I managed to get well over 1000ppm. 30-40 times higher than the "saturation" point Tom Barr had concluded.



Robert H said:


> Please tell me again what the basic conclusions were from your experiment and in a very basic way explain how you reached those conclusions, and why it is important.


My conclusions were that any/all microbubbles "persisting" in tank water (as they are blown around) can NOT be bubbles consisting of CO2 (because of the ease and speed in which CO2 dissolves in water). As for the explanation of importance, at the risk of redundancy, I refer you to my first paragraph at the top of the page.



Robert H said:


> I do not see stubborn bubbles, ever. I see bubbles that rise up to the water surface and disappear within seconds.


When I said "stubborn" bubbles", it was in the context of the microbubbles (being blown around by a powerhead) debate.


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## unirdna (Jan 22, 2004)

Bert H said:


> Dawgger, According to what Ted is saying, this shouldn't be happening??!! Or at least, that it isn't CO2.


Bert, never did I say "this shouldn't be happening". Dawgger's observations are entirely consistent with what I would expect for O2 saturated water. 

You are correct that this gas pocket is not CO2 (or at least very very little). 

Dawgger could test whether or not this pocket of air is CO2 by doing the following steps.

1. turn off the filter (water flow)
2. release this pocket of air
3. inject an equal amount of CO2 (that the air had previously occupied)
4. turn on the filter (water flow)

Then, when the "new" pocket of CO2 gas quickly dissolves, it will be obvious that the "old" pocket of air was certainly NOT CO2.


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## Georgiadawgger (Apr 23, 2004)

This is probably the case, but with my new reactor (yes probably more efficient since its twice as long now...gigantic!!), I get a much slower bubble rate that saves gas and keeps the co2 levels constant. This is testing the pH after work (5 pm), before bed (10:30) and at wake up (6:30). Same level of gas inside the reactor and same pH readings. 

Heck, if it ain't broke...don't fix it...anymore :tongue:


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## co2 (Sep 13, 2004)

Robert H said:


> Please tell me again what the basic conclusions were from your experiment and in a very basic way explain how you reached those conclusions, and why it is important.


Robert H, no offense, but you are coming off pretty argumentatively without 
"doing you're homework". Unirdna/Ted has stated the basic conclusions of his experiment several times, you just aren't picking up on them. He has made many pertinent conclusions, among them are: CO2 is much more soluble in H2O than we tend to think, that 30ppm is no where close to the saturation point of CO2 in H2O, and that Tom's micro bubbles are not CO2, but most likely O2... otherwise they would quickly dissolve. 



Robert H said:


> I do not see stubborn bubbles, ever. I see bubbles that rise up to the water surface and disappear within seconds.


If you "do not see stubborn bubbles, ever" and if you don't understand that Unirdna's thread was in response to Tom's exploitation of micro bubbles (that were supposedly CO2) in order to increase plant growth, then you are not going to grasp the point of this thread, you might want to read Tom/plantbrain's "CO2 revelations" threads in order to put this thread in it's proper context.


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## co2 (Sep 13, 2004)

I just want to ad my take on Tom's theory. The fact is that Tom observed better results with the micro bubbles, and because of his reputation I am inclined to experiment with the micro bubbles despite any reservations I have. Regardless of the science behind the micro bubbles, they may be beneficial for other reasons. I find Unirdna's thread very helpful, and I definitely learned a couple things. One of my initial concerns with the micro bubbles was... even if they do work, how could anyone evenly distribute them? Also, it was stated that less algae was seen using the MB method, how could that be? Would that be due to the MB's actually making contact with the algae? That doesn't make sense to me.


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## jimmydrsv (Apr 8, 2005)

I have been going in and out of this thread and the question i ask myself is if the conditions in which you performed your test anywhere near applicable to a real life situation.

A bottle with water and co2 is a very closed system as compared to a tank with everything that is in it. Your test basically showed how much the water can be saturated when the co2 has no out other than the water. 

I was ready to doubt tom's conclusion after initially reading this thread but then there are still lingering questions.

I have also heard from others that the micro bubble method caused increase growth and decreased algae. 

I have seen algae pop out of no where when my co2 slows down and if the method was completely baseless then one would have to had seen increased algae growth.


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## esarkipato (Jul 19, 2005)

*another experiment idea*

I'd like to see someone perform the following experiment: (I lack the instruments)

1. Measure how long a co2 bubble takes to dissolve in a TANK with little to no co2 already dissolved.

2. Measure how long a co2 bubble take to dissolve in the same TANK with 30ppm co2.

If the times are fairly comparable, I think I've been convinced.


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## Georgiadawgger (Apr 23, 2004)

esarkipato said:


> I'd like to see someone perform the following experiment: (I lack the instruments)
> 
> 1. Measure how long a co2 bubble takes to dissolve in a TANK with little to no co2 already dissolved.
> 
> ...


If we had the time...alas my grad student days are over...


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## shuks (Jul 10, 2005)

"I'd like to see someone perform the following experiment: (I lack the instruments)

1. Measure how long a co2 bubble takes to dissolve in a TANK with little to no co2 already dissolved.

2. Measure how long a co2 bubble take to dissolve in the same TANK with 30ppm co2.

If the times are fairly comparable, I think I've been convinced."
__________________


I already did this experament earlyer in this post. check it out probably in page 2 or 3


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## esarkipato (Jul 19, 2005)

shuks said:


> I already did this experament earlyer in this post. check it out probably in page 2 or 3


No offense intended, but this experiment is a little less than exact. "About 75%" is not enough to convince me. "7 seconds" versus "8 seconds" is much more convincing.


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## unirdna (Jan 22, 2004)

shuks said:


> "I'd like to see someone perform the following experiment: (I lack the instruments)
> 
> 1. Measure how long a co2 bubble takes to dissolve in a TANK with little to no co2 already dissolved.
> 
> ...



Fair enough. You want [your own style of] proof. Understandable. If I may, I would add that this experiment should be done with water NOT from a tank. Tank water (especially from planted tanks) is frequently saturated with O2. A tank that is saturated with O2 will have O2 come out of solution into a CO2 bubble (and then NOT dissolve back into the water). This is a central theme to the misunderstanding Tom's method has created, and an error that I believe shuks failed to know about during his/her own experiment.

I will work on performing this experiment, but for those of you waiting, I recommend you watch the video I made (page 1), showing how quickly CO2 CAN dissolve in water already containing 40ppm CO2.


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## esarkipato (Jul 19, 2005)

Perfectly put, unirdna. Assuming the said water has no o2, then the co2 bubbles should dissolve very quickly, no matter the concentration.


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## co2 (Sep 13, 2004)

One other thought I have is... with CO2 at 30-40ppm (with an external reactor in my case) and with medium high lighting, my stem plants grow a couple inches a day. How much more growth do we really want? Personally, I like the water to be clear, with as few bubbles as possible. The bubbles from the plants pearling are so prevalent that I wouldn't want to add free floating CO2 bubbles even if I could.


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## unirdna (Jan 22, 2004)

jimmydrsv said:


> I have been going in and out of this thread and the question i ask myself is if the conditions in which you performed your test anywhere near applicable to a real life situation.
> 
> A bottle with water and co2 is a very closed system as compared to a tank with everything that is in it. Your test basically showed how much the water can be saturated when the co2 has no out other than the water.


My test was to show one thing and one thing only, the true solubility potential of the theoretical limit of Carbondioxide in water. Theoretical limit is 1500ppm. I got it to well over 1100 ppm simply by bubbling CO2 into water. 

I'm not sure what you mean by "when co2 has no out other than the water". I did not increase pressure on the water. I did not cool the water. So, how do you figure I somehow forced a higher-than-natural amount of CO2 into the water?

Do the same experiment using Oxygen in place of CO2. Do you think you would get 1000+ppm O2 into the water doing the same. Can you achieve 1000+ dissolved oxygen in water by aerating? No you can not. Once the water reaches O2 saturation, it will resist the addition of any higher concentration. As I bubbled CO2 into the cup of water, the pH continued to drop more and more. The water was "happy" to dissolve many many ppm CO2.



jimmydrsv said:


> I was ready to doubt tom's conclusion after initially reading this thread but then there are still lingering questions.
> 
> I have also heard from others that the micro bubble method caused increase growth and decreased algae.
> 
> I have seen algae pop out of no where when my co2 slows down and if the method was completely baseless then one would have to had seen increased algae growth.


I can't say this enough. I never drew into question the effectiveness of the "microbubble" theory. I never said it would not grow plants better. I never said it would not reduce algae growth. I haven't tried it. I have no idea what it does to plant growth and algae.

What I DID call in to question was the [misunderstood] properties of CO2 solubility.


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## Laith (Jul 7, 2004)

co2 said:


> One other thought I have is... with CO2 at 30-40ppm (with an external reactor in my case) and with medium high lighting, my stem plants grow a couple inches a day. How much more growth do we really want? Personally, I like the water to be clear, with as few bubbles as possible. The bubbles from the plants pearling are so prevalent that I wouldn't want to add free floating CO2 bubbles even if I could.


I'm thinking exactly the same thing. I'm one of those that can't abide aerators in tanks so the thought of adding clouds of microbubbles in addition to the pearling is just... not on for me. But I'm not having problems getting enough CO2 into the water to provide great growth and little algae without creating a foam bath! :tongue: 

I do find the concept being discussed very interesting.


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## shalu (Jan 16, 2003)

co2 said:


> One other thought I have is... with CO2 at 30-40ppm (with an external reactor in my case) and with medium high lighting, my stem plants grow a couple inches a day. How much more growth do we really want? Personally, I like the water to be clear, with as few bubbles as possible. The bubbles from the plants pearling are so prevalent that I wouldn't want to add free floating CO2 bubbles even if I could.


well, you missed part of what Tom Barr was saying. He was saying for many "difficult", "sensitive" plants, they become easy plants with this technique. I agree with you, I don't want 4inches per day instead of 2inches per day for lots of easy weeds.


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## lumpyfunk (Dec 22, 2004)

Question about henerys law:
Does it only cover atmospheric pressures for the gases to want to create equliberum?
I understand it with a surface to atmosphere relationship. But the micro bubles (what ever they are composed of) are under more pressure then the gasses on the surface of the water. Does this matter for Henerys law?


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## unirdna (Jan 22, 2004)

lumpyfunk said:


> Question about henerys law:
> Does it only cover atmospheric pressures for the gases to want to create equliberum?
> I understand it with a surface to atmosphere relationship. But the micro bubles (what ever they are composed of) are under more pressure then the gasses on the surface of the water. Does this matter for Henerys law?


Valid question, lumpyfunk. Henry's Law is for all gas/water equilibria relationships, not just those with the atmosphere.

A concise, accurate, easy-to-understand definition can be found here.

From the pages of Georgia State University physics department.
http://hyperphysics.phy-astr.gsu.edu/hbase/kinetic/henry.html


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## jbaker6953 (Sep 18, 2005)

lumpyfunk said:


> Question about henerys law:
> Does it only cover atmospheric pressures for the gases to want to create equliberum?
> I understand it with a surface to atmosphere relationship. But the micro bubles (what ever they are composed of) are under more pressure then the gasses on the surface of the water. Does this matter for Henerys law?


Yes, the bubbles will be under the pressure equivalent to their depth in water. This will _increase_ the rate that CO2 is driven from the bubble into the water, but not by a whole lot. It takes about 33 feet of water to double atmospheric pressure. Since we are dealing with nothing over 30" in most cases, the effect is small.

The surface area of the bubble has to be taken into account. The area as very large in comparison to the volume inside. A 2mm bubble has a surface area of 12.6mm2. If you had about 32,000 of those floating around the tank, they would have a surface area equal to the surface area of the water surface in a 55-gallon tank. For those that think that is way too many, 32,000 bubbles is only enough bubbles to put about 1.8cm (a little over an inch) between each bubble spread evenly in a 55-gallon tank.


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## jbaker6953 (Sep 18, 2005)

Make that a little under an inch.


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## Matak (Aug 10, 2005)

I may be asking the fools question here but, if a tank has in excess of 30 ppm of CO2 dissolved in it, does it have any effect on the solubility of other gasses, such as O2?


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## unirdna (Jan 22, 2004)

Matak said:


> I may be asking the fools question here but, if a tank has in excess of 30 ppm of CO2 dissolved in it, does it have any effect on the solubility of other gasses, such as O2?


That's a perfectly reasonable question. The answer is no. CO2 solubility is independent of other gasses and vice versa.


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## wantplantsnotwork (Nov 28, 2004)

What an awesome thread. I like the idea of removing the gas in a reactor and replacing with a similar amount of CO2. At least it may tell us what it is not.

For a reactor in my system I use a ehiem 2229 wet dry filter that has the control float removed. Every once in a while, I have to shut off the filter and "bleed" out the collected gas. When I shut off the pump, it comes gushing out the water intake in great, huge, voluminous bursts. I have never corallated (I dont have a tank log) under what conditions the bubble gets big enough to make me purge it. My sneaking suspicion was the filter sock on the intake got fowled, slowing down the mass flow. This happens if I don't clean the prefilter as often as I should.

But maybe it's another gas (s) and the lower mdot has nothing to do with it.

Can't wait till one of you figure this out and spit out the Cliff notes!


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## Robert H (Apr 3, 2003)

> Robert H, no offense, but you are coming off pretty argumentatively without "doing you're homework". Unirdna/Ted has stated the basic conclusions of his experiment several times, you just aren't picking up on them. He has made many pertinent conclusions, among them are: CO2 is much more soluble in H2O than we tend to think, that 30ppm is no where close to the saturation point of CO2 in H2O, and that Tom's micro bubbles are not CO2, but most likely O2... otherwise they would quickly dissolve


No offense to you Craig, but you are sounding a little snobbish. I don't need to do my homework. I asked a simple question. What is the relevance of all this to the hobby? If Ted can't answer that question then fine. I invited him, NOT YOU to explain his experiment again in more simple terms. If he is not willing to do that then fine. This isn't the scientific journal.

If you think I am at a dumb level, there are many more confused people than just me. I have already gotten four emails from people who read this thread and asked me to explain it to them. Should I buy a reactor or a diffusor? Does this mean I am doing something wrong with my C02? One person has even asked to return the reactor they bought from me after reading this. This is the danger of these types of conversations. You do not realize how many people read this and what the impact is. At least Tom had an objective. Better plant growth, faster photosynthesis/pearling. I do not see a clear objective here. It is really impressive to me that someone actualy has the intellect to know the size of a bubble and be able to calculate how many bubbles could fit in a 55 gallon tank. Congratulations. But how can I use that fact to make my plants grow better?



> and that Tom's micro bubbles are not CO2, but most likely O2


I don't think that has been established at all. I thought Ted even acknowledged this was a suggestion by him that can not ve substantiated at this time. Moving on:


Dr. David Huebert wrote a paper on plant physiology, and says the following:



> Dissolved Inorganic Carbon (DIC) in freshwater occurs as four different species in equilibrium with one another. The four species of DIC are; carbon dioxide (CO2), carbonic acid (H2CO3), bicarbonate (HCO3-), and carbonate (CO3=). The total amount of DIC largely determines the buffering capacity of freshwater, and the ratio of these species with one another largely determines the pH. Carbon dioxide dissolves readily in water. At air equilibrium, the concentration of CO2 in air and water is approximately equal at about 0.5 mg/L. Unfortunately, *CO2 diffuses about ten thousand times slower in water than in air.* This problem is compounded by the relatively thick unstirred layer (or Prandtl boundary) that surrounds aquatic plant leaves. The unstirred layer in aquatic plants is a layer of still water through which gases and nutrients must diffuse to reach the plant leaf. It is about 0.5 mm thick, which is ten times thicker than in terrestrial plants. The result is that approximately *30 mg/L free CO2 is required to saturate photosynthesis in submerged aquatic plants*.


How do these facts support what you are saying?


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## esarkipato (Jul 19, 2005)

Just because co2 is not the limiting factor in photosynthesis doesn't mean it won't dissolve readily into the water. 

if co2 is 30ppm or mg/l, then light, or nutrients become limiting factors in photosythesis, right? In order to increase growth, you need more light OR more nutrients OR both.

So what possible good would the microbubbles be, even if they are co2? IF CARBON IS NOT THE LIMITING REAGENT, WHAT IS THE BENEFIT OF MORE CARBON?


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## esarkipato (Jul 19, 2005)

> *Carbon dioxide dissolves readily in water*. At air equilibrium, the concentration of CO2 in air and water is approximately equal at about 0.5 mg/L. Unfortunately, CO2 diffuses about ten thousand times slower in water than in air. This problem is compounded by the relatively thick unstirred layer (or Prandtl boundary) that surrounds aquatic plant leaves. The *unstirred layer in aquatic plants is a layer of still water through which gases and nutrients must diffuse to reach the plant leaf.*


I believe the first statement supports Ted's experiment, yet it gives no qualifiers as to any concentrations.

Just a thought, here. I do not doubt that Tom witnessed supurb growth, even better than ever growth. I just wonder: by providing excess water movement, MB or no MB, would this decrease the thickness of the Prandtl boundary? That would increase the uptake rate of co2, as well as other nutrients possibly even light?


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## SCMurphy (Oct 21, 2003)

Robert H said:


> No offense to you Craig, but you are sounding a little snobbish. I don't need to do my homework. I asked a simple question. What is the relevance of all this to the hobby? If Ted can't answer that question then fine. I invited him, NOT YOU to explain his experiment again in more simple terms. If he is not willing to do that then fine. This isn't the scientific journal.


Wow, I really wanted to avoid spoon-feeding you, but, after your polite PM answer the other day, and this thoughtful response, I guess it is actually necessary. 

Why the experiment, to illustrate that a claim being made was not inline with physical laws. This was done to help isolate what should be made as a claim.

What is important about the discussion to you as a hobbiest? I'm covering all three of the CO2 Bubble Blast threads here. The important thing is that not only do you have to do a good job of dissolving the CO2, but you have to do a good job of dispersing it through the tank. The micro-bubbles are the visual cue in some instances that the CO2 laden water is being dispersered. Also, if you do something to increase the current past the plant leaves, with the CO2 laden water, then you will see happy plants, all other things necessary for good plant growth assumed to be in shape.

If this is all you take away from this discussion you are doing well. 

Now, please be polite in your responses to people on this forum. If someone else wants to answer your question, they can. If someone doesn't want to answer and feed the flame you are fanning, kudo's to them. If someone politely suggests something in a PM to save you some grief, think about it before someone else on the forum suggests something similar in the thread.


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## SCMurphy (Oct 21, 2003)

esarkipato said:


> Just because co2 is not the limiting factor in photosynthesis doesn't mean it won't dissolve readily into the water.
> 
> if co2 is 30ppm or mg/l, then light, or nutrients become limiting factors in photosythesis, right? In order to increase growth, you need more light OR more nutrients OR both.
> 
> So what possible good would the microbubbles be, even if they are co2? IF CARBON IS NOT THE LIMITING REAGENT, WHAT IS THE BENEFIT OF MORE CARBON?


We aren't discussing the other parameters here, the assumption of this discussion is that all the other parameters are inline for good plant growth. A reasonable assumption in the hypereutrophic conditions of an IE tank. This does make light and C the limiting agents.



esarkipato said:


> Just a thought, here. I do not doubt that Tom witnessed supurb growth, even better than ever growth. I just wonder: by providing excess water movement, MB or no MB, would this decrease the thickness of the Prandtl boundary? That would increase the uptake rate of co2, as well as other nutrients possibly even light?


Maybe not light, directly, but yes, you have the idea, increase the current past the plants with enough CO2 available, and you can help the plants overcome CO2 diffusion limitations. The plans do also benefit in from increasing the current to increase the uptake of the other nutrients.


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## jimmydrsv (Apr 8, 2005)

unirdna said:


> So when you see gas build up in a reactor, you should NOT be asking, "why does the CO2 in my tanks get to ignore well known solubility constants?". You should be asking,"since I know that gas can NOT be CO2 because of how easily and quickly CO2 dissolves, what other gas(ses) could that be and by what means did it (they) get in my reactor?


I think you made a jump somewhat here. If the bubbles are caused by excessive O2 in the water, it doesn't mean that there can't be CO2 in it.

If the water is super saturated in oxygen then it would be looking for a way out or it would start coming out of solution. We have seen this behaviour as pearling.

With co2 coming into the reactor as gas(bubbles), the oxygen super-saturated water could very likely be diffusing into the incoming bubbles. This would cause the co2 to become a o2/co2 mix of gas. This would give reason to why o2 would clump up inside the reactor(because there is gas for it to diffuse into).

With co2 more willing to dissolve into air than water, this tendency might outweigh its ability and tendency to fully dissolve into the water and cause an amount of the co2 to be retained in the bubble.


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## esarkipato (Jul 19, 2005)

Okay, I understand that the assumption is plently of light and nutrients. I understand that 30 ppm of co2 is recommended (or scientifically postulated) to produce max. photosynthesis. 

What Tom is saying is that you can acheive SUPER-maximum photosynthesis with micro-co2-bubbles + current?

The only thing I'm convinced of now is that I will not care about this discussion until i've reached the FIRST stage of maximum photosynthesis LOL 

(but for the record I doubt, after Ted's experiment, that the microbubbles are composed of co2.)


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## unirdna (Jan 22, 2004)

Robert H said:


> If Ted can't answer that question then fine. I invited him, NOT YOU to explain his experiment again in more simple terms. If he is not willing to do that then fine. This isn't the scientific journal.


Robert, I did. I've taken the time to respond to all queries, regardless of redundancy. Please look back to pg 4 to find your answer.



Robert H said:


> If you think I am at a dumb level, there are many more confused people than just me. I have already gotten four emails from people who read this thread and asked me to explain it to them. Should I buy a reactor or a diffusor? Does this mean I am doing something wrong with my C02? One person has even asked to return the reactor they bought from me after reading this. This is the danger of these types of conversations. You do not realize how many people read this and what the impact is.


Oh, yes I do realize how many people read this. In fact, here's is a quote from one of my posts in direct response to you. 



unirdna said:


> "Tom may have been right in the past re: other aspects of the hobby, but he was quite wrong this time. I knew that contradicting him would bring opposition from his followers. Some blind. Some inflammatory. Some honest. I knew it would start as an uphill battle, but I also knew that eventually, the evidence would speak for itself. If I would have overheard the conversation at a local pub, I wouldn't have felt the need to correct (actually, that would be quite rude), but this forum is a massive hub for information. NOT posting, was out of the question."


To answer the concerns of your potential and current customers, I would say that I use both reactors and diffusers with great success.

I did not start this thread to create confusion; I started it to clarify the confusion that Tom Barr started re: CO2 Solubility. Tom's claims went against the common laws of physics. Had we accepted his claims, the science behind the hobby would have taken a very large step backwards.



Robert H said:


> At least Tom had an objective. Better plant growth, faster photosynthesis/pearling. I do not see a clear objective here. It is really impressive to me that someone actualy has the intellect to know the size of a bubble and be able to calculate how many bubbles could fit in a 55 gallon tank. Congratulations. But how can I use that fact to make my plants grow better?


All due respect, Robert, your sarcasm is not helpful. I'm doing my best to convey the information I have re: CO2 Solubility. My time is as precious as the next person's. It takes me time to write responses. Please give me the respect of reading my responses thoroughly. I've stated my purpose/objective many times, directly, to you. Please reread those responses, and if you are still unclear, quote me, so I can know what part of my response to this question confused you. 



Robert H said:


> I don't think that has been established at all. I thought Ted even acknowledged this was a suggestion by him that can not ve substantiated at this time.


I've stated numerous times that the persistant microbubbles being blown around the tank are NOT Carbondioxide. Here's the order:

1. Tom claims that microbubbles [of CO2] can be blown around the tank, undissolved because when CO2 reaches 30ppm, CO2 becomes more difficult to dissolve.

2. I've shown that CO2 does NOT become measurably significant to dissolve at 30ppm, because CO2 is only at .2% of the solubility potential. In other words, water will dissolve 99.8% more CO2 than that amount (30ppm) where Tom Barr is claiming that CO2 becomes difficult to dissolve. Therefore, these microbubbles are NOT CO2.




Robert H said:


> Dr. David Huebert wrote a paper on plant physiology, and says the followingissolved Inorganic Carbon (DIC) in freshwater occurs as four different species in equilibrium with one another. The four species of DIC are; carbon dioxide (CO2), carbonic acid (H2CO3), bicarbonate (HCO3-), and carbonate (CO3=). The total amount of DIC largely determines the buffering capacity of freshwater, and the ratio of these species with one another largely determines the pH.


All this is exactly consistant with what I'm saying re: the Solubility of CO2, and what we know. If there is a part of this portion of the quote that you do not understand, ask. 



Robert H said:


> Dr. David Huebert: "Carbon dioxide dissolves readily in water".


Don't miss this tiny part. It's a major theme of this thread .



Robert H said:


> Dr. David Huebert: "At air equilibrium, the concentration of CO2 in air and water is approximately equal at about 0.5 mg/L".


Yep, that's why we need to dissolve CO2 directly into our water. Because the partial pressure (ther's Henry's law again) of CO2 in the atmosphere reaches equilibrium with water at only .5ppm



Robert H said:


> Dr. David Huebert: "Unfortunately, CO2 diffuses about ten thousand times slower in water than in air".


Bam! Confusion. Right? Dr. David Huebert is exactly right. CO2 does DIFFUSE 10,000 times more slowly in water than air. This means that it is 10,000 times more difficult to disperse CO2 in water, NOT (I repeat, NOT) that CO2 is 10,000 times more difficult to DISSOLVE in water. This is why it would be benificial to add water current to our aquaria (which we all do). Current ensures that CO2 enriched water contiues to flow over plant tissues. And low and behold, current is what Tom Barr added to his tank when he decided to blow microbubbles around :icon_idea , and claimed to see increased growth.

*Sean hit the nail on the head with this quote:*



SCMurphy said:


> The important thing is that not only do you have to do a good job of dissolving the CO2, but you have to do a good job of dispersing it through the tank. The micro-bubbles are the visual cue in some instances that the CO2 laden water is being dispersered. Also, if you do something to increase the current past the plant leaves, with the CO2 laden water, then you will see happy plants, all other things necessary for good plant growth assumed to be in shape.






Robert H said:


> Dr. David Huebert: "This problem is compounded by the relatively thick unstirred layer (or Prandtl boundary) that surrounds aquatic plant leaves. The unstirred layer in aquatic plants is a layer of still water through which gases and nutrients must diffuse to reach the plant leaf. It is about 0.5 mm thick, which is ten times thicker than in terrestrial plants. The result is that approximately 30 mg/L free CO2 is required to saturate photosynthesis in submerged aquatic plants".


I made no attempt to discuss the Prandtl Boundary in this thread. In fact, I've spent considerable energy trying to keep the conversation on topic: CO2 Solubility.

The Prandtl boundary is such a massive topic, it deserves its own thread.


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## m.lemay (Jul 28, 2002)

I'm not gonna enter into this debate about what the bubbles are, because I don't know.

I do know that good circulation or a gradual current is vitally important to the exchange of nutrients at the leafs Prandtl boundary. Poor circulation equals lackluster growth and algae in many cases. This has been my observation.

Marcel


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## unirdna (Jan 22, 2004)

jimmydrsv said:


> I think you made a jump somewhat here. If the bubbles are caused by excessive O2 in the water, it doesn't mean that there can't be CO2 in it.
> 
> If the water is super saturated in oxygen then it would be looking for a way out or it would start coming out of solution. We have seen this behaviour as pearling.
> 
> ...


This is a very good observation. Allow me to explain why the amount of CO2 gas (with respect to other gasses, such as O2) would be negligible.

Henry's Law is described as such:

Concentration of dissolved gas = Partial pressure of gas x Solubility coefficient

The solubility coefficient is constant, so, as Henry's Law shows, the amount of concentration is directly proportional to the partial pressure of that gas.

It is known that the air (atmosphere) has 300ppm CO2, and that the equilibrium with the atmosphere, with respect to dissolved CO2 in water, is .5ppm. So, for an aqarium at 30ppm CO2, Henry's Law shows us that the "air pocket" in the reactor would reach equilibrium at 18,000ppm CO2.

Thus, the air pocket in question would reach equilibrium at 1.8% CO2. Not much.


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## jimmydrsv (Apr 8, 2005)

Wait, i lost you a bit. A 18,000ppm co2 air bubble is not much? 

1.8% co2 gas as opposed to .00003% co2 in water seems more than a negliable amount.


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## unirdna (Jan 22, 2004)

jimmydrsv said:


> Wait, i lost you a bit. A 18,000ppm co2 air bubble is not much?
> 
> 1.8% co2 gas as opposed to .00003% co2 in water seems more than a negliable amount.


An 18000ppm CO2 air bubble is not much with respect to the rest of the gas in that bubble. 

If I'm correct, your concern was that I was not taking into consideration that the air pocket in a reactor could have a substantial amount of undissolved CO2 in it. I showed that it _could_ occupy a maximum amount of 1.8% of the total gas (for aquaria with 30ppm CO2 in the water). To me, if the air pocket is 98+% other gasses, it certainly isn't much CO2.

What's more is that even if that air pocket DOES have 18000 ppm CO2 (occupying 1.8% of the total bubble), it is AT EQUILIBRIUM. Meaning, that the 18000ppm CO2 will NOT dissolve into the water (meaning that any CO2 added will HAVE to dissolve because the gas/water is already at equilibrium), but this is contingent that the other gasses (oxygen) maintain their concentration in the reactor as well. Only when O2 concentration in the aqariua is lowered (at night) can that 1.8% CO2 dissolve back into solution as well. This is because as O2 levels in the aqarium drop below saturation (at night), O2 in the reactor will begin dissolving back into solution. Thus, the ppm of the remaining CO2 would rise (with respect to the concentration of O2), and consequently dissolve back into solution as well.

Now, read that again, and make sure you understand each step before going to the next . It will make sense if you take it slowly.

Also, you forgot to multiply .00003 * 100 to get .003%.


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## jimmydrsv (Apr 8, 2005)

That would mean that co2 has to be diffused out of these bubbles to reach the level of equilibrium you stated. 

A pure co2 bubble when released would have the high co2 potential that tom stated but it is highly unlikely to have that same potential when it actually comes to contact a plant due to co2 going out and o2 coming in as it makes its journey.

So, how long before a pure co2 bubble reaches equilibrium and becomes useless?

How long does it take for a bubble to go from 99...% to 2% and can the bubble be utilized in between seems like the question most relevant to Tom's method.

Also not in consideration yet is the equilibrium inside the reactor and the equilibrium when it is inside the tank.


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## unirdna (Jan 22, 2004)

jimmydrsv, 

I like that you building on what we've learned. 

How long a bubble goes from 99..% to 2% depends on many things. One of which is whether or not other gasses are satruated in the aqarium. This is because if no other gasses diffuse into the bubble, CO2 will always stay at 99..% (until it dissolves completely). Only if other gasses go in, can that percentage drop.

Regardless, even if the bubble takes on other gasses, "permitting" it to also carry a small percentage of CO2, that CO2 is NOT going to dissolve into solution (unless the other gasses dissolve as well, or the ppm of CO2 in the tank lowers).

I understand completely what you mean by "CO2 potential", but caution against too much language of that sort, because I've noticed it can create a lot of confusion .


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## bharada (Mar 5, 2004)

So how about setting up some capture bells? Place them so that they capture bubbles at various points in the tank. Once enough bubbles have been collected you can analyze the it and see what the composition is the farther away from the diffuser you get. If Ted's theory is correct then at the opposite end of the tank the gas collected should be nearly all O2/N2 or some other inert gas.


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## unirdna (Jan 22, 2004)

bharada said:


> So how about setting up some capture bells? Place them so that they capture bubbles at various points in the tank. Once enough bubbles have been collected you can analyze the it and see what the composition is the farther away from the diffuser you get. If Ted's theory is correct then at the opposite end of the tank the gas collected should be nearly all O2/N2 or some other inert gas.



I like the idea, Bill. However, my evidence suggest that CO2 dissolves too quickly to get any appreciable difference in the 3 bells.. In other words, [if the bells collect any gas] I thinkthey will all be collecting O2/N2 or some other inert [saturated] gas, especially since there is current passing by the bells.

I'm still working on setting up an experiment to show just HOW quickly CO2 will completely dissolve when using a diffuser and current. I'm going to use reconstituted RO/DW to do this because this water will not be saturated with inert gasses (like tap water). I will use a YSI Temp/DO meter to make sure the water is well below O2 saturation.


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## jbaker6953 (Sep 18, 2005)

*Summary*

These thread are getting long and difficult to follow as evidenced by some posts indicating same. It is important that we not lose sight of the focus.

Tom sees increased growth and pearling after CO2 bubble-blasting. Tom hypothesizes that this is due to increased CO2 availability. Group is investigating whether or not the microbubbles actually are CO2. The practical implications are that if the bubbles are CO2 we can achieve increased growth and pearling by the CO2 bubble blasting method, and if they are not CO2 then the increased growth and pearling are due to factors other than CO2. Discovering what is behind the observed phenomena will advance the knowledge of freshwater plant-keeping. That is the point.

It's that simple.

PS - As far as people being impressed (albeit sarcastically :icon_roll ) by the calculation of bubble surface area, they shouldn't be. It takes about 45 seconds to do the math:

mm^3/bubble = (1219mm*330mm*508mm)/((1219mm*330mm)/4π1^2)

In solving that you get all the information that I posted about that. So, no, it's not that someone spent a long time doing pointless math ... it's that someone just took the couple of seconds to explain something with facts instead of arguing about it.


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## Trapper (Dec 9, 2004)

plantbrain said:


> '
> 
> Adding CO2 to a reactor(with bioballs etc) vs adding it to a tank are two quite different methods of adding CO2......... and 2 minutes is a long time concerning persistence...............
> 
> ...


A propos of perhaps nothing, what do you think of these thought experiments:

Consider introducing two bubbles of gas at the bottom of an arbitrarily deep and large vessel of water. Bubble #1 is pure CO2. Bubble #2 is 50:50 CO2 and helium.

In the first iteration of the thought experiment, the water is pure and degassed. In the second, it's got some gases dissolved in it.

In the first round, I think it's pretty safe to say that bubble #1 will disappear before it hits the surface; this is so because CO2 is freely soluble in pure water. The CO2 bubble will travel through enough water completely to dissolve it. Bubble #2 will hit the surface devoid of its CO2; this so because helium is insoluble and because the water, as stipulated, is degassed. And furthermore bubble #2 will contain only He and water vapor when it hits the surface.

In the second round, bubble #1 will entirely disappear (assuming the water is not at CO2 saturation). Bubble #2 will hit the surface composed of He, water vapor, and whatever other gases were already present in the water. That would include CO2 if any were dissolved to begin with.

FWIW,
Trapper


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## foob (Oct 13, 2005)

Thanks for the experiment. It helped me understand some basics and the results are a lot better than jumping to conclusions from short observations.


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## shalu (Jan 16, 2003)

I don't think round 2, bubble #1 will completely disappear if the conclusion for bubble #2 is true. During the process of CO2 dissolving for bubble #1, degassing of other gas from water occurs simultaneously into this bubble and the bubble will not be pure CO2 anymore, so you will still end up with some tiny bubbles.


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## scolley (Apr 4, 2004)

Bump.

The new Barr Report is out, dealing with this topic. If you subscribe, I suggest you take a look.


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## anonapersona (Oct 19, 2002)

shuks said:


> At first the co2 bubbles would dissolve about 95% of their mass. The Next day, I mesured c02 levels about 20ppm. I knoticed that the bubbles wernt disolving as much as they did before. I would say that with a co2 level of 20 ppm, the bubbles would only dissolve about 75 % of it's mass.


When you are looking at the volume dissolved, be sure to account for the geometry correctly. Volume decreases with the cube of the diameter, so, for example, if a bubble is reduced to 25% of the original diameter the volume is 1.5% of the original volume. 

My point is that once the bubble passes the point of 75% reduction in diameter, any more is irrelavant for most purposes, since 98.5% is gone by then.

So, when you start with tiny bubbles, it is quite possible that you still have a certain % of the volume remaining but you just can't see it.


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## anonapersona (Oct 19, 2002)

unirdna said:


> Simply bubbling CO2 into water, I managed to get well over 1000ppm. 30-40 times higher than the "saturation" point Tom Barr had concluded.


Perhaps there is a saturation point for water that contains plants! What if water with very high CO2 levels was rapidly reduced to lower levels by the presence of plants??


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## anonapersona (Oct 19, 2002)

wantplantsnotwork said:


> What an awesome thread. I like the idea of removing the gas in a reactor and replacing with a similar amount of CO2. At least it may tell us what it is not.
> 
> For a reactor in my system I use a ehiem 2229 wet dry filter that has the control float removed. Every once in a while, I have to shut off the filter and "bleed" out the collected gas. When I shut off the pump, it comes gushing out the water intake in great, huge, voluminous bursts. I have never corallated (I dont have a tank log) under what conditions the bubble gets big enough to make me purge it. My sneaking suspicion was the filter sock on the intake got fowled, slowing down the mass flow. This happens if I don't clean the prefilter as often as I should.


Could be cavitation at the pump which breaks gasses out of solution when the pressure drop is too large. Restrictions at the pump inlet will do this. Higher gas saturation makes this happen more easily.


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## anonapersona (Oct 19, 2002)

esarkipato said:


> I just wonder: by providing excess water movement, MB or no MB, would this decrease the thickness of the Prandtl boundary? That would increase the uptake rate of co2, as well as other nutrients possibly even light?


Yes, that is worth knowing, whether the flow rate in the test tank was kept constant.


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## unirdna (Jan 22, 2004)

anonapersona said:


> Perhaps there is a saturation point for water that contains plants! What if water with very high CO2 levels was rapidly reduced to lower levels by the presence of plants??


I thought this question came up in this thread before? Maybe it was a different thread.

Photosynthesis has its limits.

Consider the following:

How much CO2 is in 1000ppm for a 75 gallon (284 liter) tank?

Well, 1000ppm equals 1 gram per liter. So 1000 ppm CO2 injected into a 75 gallon tank would work out to 284 grams (or, just over 3/5 pound). If plants could rapidly reduce that CO2, it would mean that they are incorporating it into their tissues. This means that we could expect to see the plants gains that mass in dry weight. Ever dry your plants out? Not much weight. That much dry weight would equal many many many stems of plants.

The point is that plant growth could not keep up with such a level of CO2 injection. And the truth is that in most cases, far more CO2 is lost to the atmosphere than is incorporated into plant tissue. If this wasn't the case, everyone who runs a steady bpm would run into massive pH swings. My pH lowers .1 at night vs. day.


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## baj (Sep 16, 2004)

unirdna said:


> I thought this question came up in this thread before? Maybe it was a different thread.
> 
> Photosynthesis has its limits.
> 
> ...


I second that, plants probably do not keep up with the rate of injection. 

Could it be that the turbulent flow in the reactor chamber ends up in forcing microbubbles to form just because the gas wants to move into the low pressure area created by the turbulent flow? 

1) The water being forced out from a narrow opening into a larger chamber could create a low pressure zone at the mouth of the opening.
2) CO2 needs to build up to a critical concentration inside the tube, I dont know the numbers because I dont know the rate constants and anyway, any guess would be meaningless unless it is standardized to temperature, etc.
3) The co2 would tend to diffuse into the low pressure zone inside the reactor.
4) My line of thinking is, yes co2 is fully dissolvable for the case at hand. But co2 would just as easily want to diffuse out into the quasi-vacuum and occupy that space, simply because the pp of the gas in solution is obviously higher than the pp in the quasi-vacuum.
5) The co2 microbubble could just as easily be dissolved back in the turbulent flow, however, could it be possible that if the rate at which the bubbles are formed by cavitation equals the rate at which co2 is being dissolved into the solution (since we are still injecting co2), then the bubbles could persist long enough for it to be blown out of the reactor?


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## defdac (Dec 28, 2003)

Ahh.. Cavitation! Now we're getting somewhere =)


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## jgc (Jul 6, 2005)

If the bublles are c02, but caused by cavitation - Shouldn't they disolve quickly after they leave the reactor? Cavitation might be making the bubbles, but they will need to be a large percentage other gasses to be persistant outside of the reactor.

Of course I could be wrong too


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## baj (Sep 16, 2004)

jgc said:


> If the bublles are c02, but caused by cavitation - Shouldn't they disolve quickly after they leave the reactor? Cavitation might be making the bubbles, but they will need to be a large percentage other gasses to be persistant outside of the reactor.
> 
> Of course I could be wrong too


Of course not, you could be right  given that these big bubbles of co2 dissolve rather quickly, the little bubbles should dissolve as well. I brushed up on a few things and I am beginning to like the idea of o2 at saturation levels diffusing into the co2 bubble, it is definitely possible. And o2 already at saturation means that the 02 bubbles may persist longer as well. Moreover, it is the same tank water that is being cycled through the reactor, so since co2 wont displace the dissolved o2, it could just as well be that the bubbles forming due to cavitation are o2 themselves, or even if co2 bubbles form, they dissolve and o2 diffuses in. It is another idea and a possibility, just as ionized radiation at the earth's pole may be changing the spin of the o2 molecules such that the mid-afternoon tide at the straits of gibraltar influence the o2 bubbles to congregate, but the o2 diffusing into co2 seems more plausible.

Why dont we have a drip irrigation system? instead of water we use co2. Use lots of pipes with holes buried in the substrate, but not fully buried and pump in co2 through these pipes so a stream of bubbles rise up from the substrate towards the surface, that way, with a little tweaking we can have zillions of co2 bubbles over, under and around plant leaves, stems , etc or is that getting too close to emersed setups :tongue:, inject so much co2 that the tank is essentially one massive co2 bubble with a thin film of water hanging on only due to surface tension.


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## BlueRam (Sep 21, 2004)

Hi. ppm = mg/kg or mg/l 

so .284 g or ~1/4 a paperclip.




unirdna said:


> How much CO2 is in 1000ppm for a 75 gallon (284 liter) tank?
> 
> Well, 1000ppm equals 1 gram per liter. So 1000 ppm CO2 injected into a 75 gallon tank would work out to 284 grams (or, just over 3/5 pound).


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## jgc (Jul 6, 2005)

I started running a bubble this last week - plus have watched my plants pearl for some time. Seems to me that air or o2 bubbles tend to rise fairly quickly. What would cause the bubbles to rise more slowly - or is that just a function of "atomizing" the bubbles.


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## unirdna (Jan 22, 2004)

BlueRam said:


> Hi. ppm = mg/kg or mg/l
> 
> so .284 g or ~1/4 a paperclip.


Your critique is incorrect. 

1000ppm = 1000mg/L = 1g/L. 

75g tank = 284L.

Therefore, 284g CO2 in the entire tank (with 1000ppm CO2).

If CO2 was equal to 1ppm in the tank, then yes, there would be .284g.

Read back further to anonapersona's post for clarification as to what brought about such calculations.

Ted


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## unirdna (Jan 22, 2004)

jgc said:


> I started running a bubble this last week - plus have watched my plants pearl for some time. Seems to me that air or o2 bubbles tend to rise fairly quickly. What would cause the bubbles to rise more slowly - or is that just a function of "atomizing" the bubbles.


If you bubble CO2 directly into a tank, you will notice that CO2 bubbles decelerate as they rise. This is because they are quickly dissoving (shrinking). The viscosity of the water has a greater effect on smaller bubbles. 

Air bubbles rise quickly because they do not dissolve (any appreciable amount of gas) on their way to the surface. Additionally, if you happen to have a plant the lets out a steady stream of small, O2 bubbles, pay attention to those bubbles as they slowly rise to the top of the tank. They grow! This is due, in small, part, to decreased water pressure (as the bubble rises to the top, less head pressure is exerted on it). But, the head pressue of even the deepest tank is far less than one ATM. In other words, bubbles at the bottom of your tank are under only a fraction more pressure than those at the top. 

The reason I say this, is because you may notice that in photosynthetically active tanks (O2 saturated) these small bubbles tend to double their diameter. This, of course, equates to many times the original volume. In other words, those bubbles are "gathering" gas. O2?

Take a look.

Ted

*edit: If you are saying that air bubbles are now rising more slowly, we would need more info re: your setup. Unless your water is depleted of O2 or N2, those bubbles should not be dissolving (shrinking). More likely, your air stone is producing smaller bubbles [than expected]? More info is definitely needed.


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## SPC (Jan 14, 2008)

Thanks for the excellent information Ted, and for those who helped with the explanations on this topic. Did you ever get around to testing what the air is that is left over in the top of the reactor.



scolley said:


> Bump.
> 
> The new Barr Report is out, dealing with this topic. If you subscribe, I suggest you take a look.


You lost me here, scolley. Why would the members of this site need to read the Barr Report in order to find out information "dealing with this topic"? IMO if Tom, or anyone else who participated in this thread, has a comment, then shouldn't they post it to this thread?

Steve


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