# CO2 and O2



## Jim Miller (Dec 24, 2002)

Excessive concentration of CO2 in water prevents the gills from transferring CO2 from internal to water. 

Hemoglobin then can't absorb O2 from water.

Suffocation then results regardless of O2 availability. 

Jim


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## BlueJack (Apr 15, 2011)

O2 and CO2 are separate. Amounts of one does not affect the other. In other words, more O2 doesn't push out CO2.

Running O2 probably creates bubbles though that "pop" at the surface....making it more difficult to keep CO2 in the water.


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## tharsis (Oct 9, 2009)

so what is the limit for CO2 concentration? 

30 ppm is desired but I have read that some people have run upwards of 40-50 ppm?


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## VeeSe (Apr 16, 2011)

it is relative, meaning that higher O2 levels will allow fish to tolerate more CO2


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## kevmo911 (Sep 24, 2010)

Well, in theory, 40-50ppm CO2 is somewhere around the limit for many types of fauna ...but it doesn't really matter for our purposes. Unless you have some very expensive test equipment, you don't know what your concentration actually is.

Your best bet is to get a drop checker with 4dKH and pH indicator solution, up your CO2 until you get greenish-yellow by the end of the lighting period (which might mean you have somewhere between 20 and 40ppm - maybe), and then daily tweak the CO2 up just a tiny bit more until your fish or inverts start stressing out. Then dial it back a notch, and you have your limit.

Or, just aim for "Mountain Dew", assume it's good enough, and move on  Oh, and either way, increased surface agitation, while allowing dissolved CO2 to gas out faster, will also insure that you've got enough dissolved O2 in the column. So, when your fish start to show signs of stress, at least you know it's not an O2 issue.


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## tharsis (Oct 9, 2009)

VeeSe said:


> it is relative, meaning that higher O2 levels will allow fish to tolerate more CO2


but that is the opposite of what the previous posters just wrote 

And essentially what my initial question was asking...

CO2 inhibits the uptake of O2 through the gills because hemoglobin prefers CO2 to O2, but.... if you increase the O2 concentration, will the greater difference in conc. between the water and the fish's blood help with binding of oxygen thus increasing the lethal concentration of CO2?

Kevmo:

I currently don't have any fish in the tank as I wanted to run some tests on the rates of plant growth. When I did have fishies, my DC was more on the yellow side with the 4dkh solution. I would start it about an hour before lights on and it would be at my chosen conc about an hour into my photoperiod. I agree about the usefullness of the DC's and it is really just an estimate with a lot of variables. 

I was AND still am diffusing it through a cerges style reactor, so I do not have CO2 bubbles in my tank. I have read that misting is more efficient for co2 uptake in plants therefore you would not need as high of a co2 conc...is this correct?

EDIT:

With the fish gone, i have been blasting CO2, and the DC is basically pee yellow 24/7 and I gotta say I am getting wonderful growth  Clearly fish would not last very long in this scenario so i was wondering if increasing the Oxygen would allow me to theoretically run higher CO2 concentrations without gassing any fish.


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## VeeSe (Apr 16, 2011)

I don't think I'm contradicting what they were saying. BlueJack said that adding CO2 doesn't push out O2, not that increasing O2 levels wouldn't help your fish tolerate more CO2. However, I don't think you can take this to "pee yellow" extremes even if you agitate your water surface well to oxygenate your water. Hope that helps!


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## BlueJack (Apr 15, 2011)

Jim Miller said:


> Hemoglobin then can't absorb O2 from water.
> 
> Suffocation then results *regardless* of O2 availability.
> 
> Jim


^ That


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## HD Blazingwolf (May 12, 2011)

TEST KIT http://www.fondriest.com/products/hach_143601.htm (200 tests 35 bux) 

also mr barr may butt in but c02 can easily be 5-10 times the concentration of o2 and be totally safe, c02 exchanges 20 times easier than o2,(that's how respiration works, c02 has to be exchanged in order for o2 to be absorbed) if there isnt more c02 in the water column than o2, guess what, respiration becomes difficult.. Fish work much the same as we do just underwater. the lethal dose of c02 to a human is 100,000 ppm or 10% of total air, the suggested dose is 1500ppm and current air quantity is LOWER than the suggested dose, currently at 380ppm avg. the lethal dose is 263 times what current levels are. more o2 can mean more c02 relatively. getting it there however is inefficient, thus the general 30ppm rule of thumb. every plant is different to a degree and so are fauna. my tank hovers at 45ppm and everyone has beautiful coloration, just had swordtail fry the other day, good eating habbits, no disease..


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## tharsis (Oct 9, 2009)

HD Blazingwolf said:


> TEST KIT http://www.fondriest.com/products/hach_143601.htm (200 tests 35 bux)
> 
> also mr barr may butt in but *c02 can easily be 5-10 times the concentration of o2 and be totally safe*, c02 exchanges 20 times easier than o2,(that's how respiration works, c02 has to be exchanged in order for o2 to be absorbed) if there isnt more c02 in the water column than o2, guess what, respiration becomes difficult.. Fish work much the same as we do just underwater. the lethal dose of c02 to a human is 100,000 ppm or 10% of total air, the suggested dose is 1500ppm and current air quantity is LOWER than the suggested dose, currently at 380ppm avg. the lethal dose is 263 times what current levels are. *more o2 can mean more c02 relatively*. getting it there however is inefficient, thus the general 30ppm rule of thumb. every plant is different to a degree and so are fauna. my tank hovers at 45ppm and everyone has beautiful coloration, just had swordtail fry the other day, good eating habbits, no disease..


So you are saying that you CAN increase O2 to increase the tolerable levels of CO2? 

In order to maintian your 45 ppm, how are you diffusing CO2? Do you have any surface agitation/O2 addition to help?

EDIT: Also would decreasing the temperature of the water result in greater possible CO2 concentration since the O2 saturation will increase? A tank temp of 70F vs 80F corresponds to an O2 saturation of ~ 8 and 9 respectively, therefore assuming that 5x the CO2 concentration is acceptable, that leads to CO2 ppm of 45 instead of 40...


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## HD Blazingwolf (May 12, 2011)

yes, however trying to introduce more c02 and more o2 leads to wasted materials, you can safely grow almost anny plant at 30pppm of c02. that being said, i have a fine pore bubble stone and and koralia 425gph pointed slightly up for agitation, plus a 1/2 inch drop from my spray bar at 210gph measured. c02 diffusion is done by a cerge reactor.

note if ur plants arent using the extra c02 its pointless


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## tharsis (Oct 9, 2009)

hmmm...so 30 ppm should work regardless of light intensity? I figured if you are under very high light (lets say 4 x t5ho bulbs) 30 ppm of CO2 would not be enough to balance that.


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## VeeSe (Apr 16, 2011)

You could just take out some of the bulbs. You can pretty much grow anything even if you remove half the bulbs.


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## tharsis (Oct 9, 2009)

I know...I can also raise the fixture and reduce the photoperiod but I am curious about this from an academic standpoint.

Is it possible to be CO2 limited at 30 ppm?


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## plantbrain (Dec 15, 2003)

tharsis said:


> so what is the limit for CO2 concentration?
> 
> 30 ppm is desired but I have read that some people have run upwards of 40-50 ppm?


I have 60-80ppm CO2 in one tank

Respiration is both the O2 and the CO2, not just one.

For example, many folks who do not use CO2, can kill fish and stress them with low O2.

That has little to do with CO2.

Higher O2 will help, and more moderate degassing will prevent the CO2 from building up too high, it will rise more gradually and top out.

So good current and surface movement ain't a bad idea.........if you care about the fish. Problem is, many assume that their relative measure of 30ppm etc is accurate, it's not.


Same with O2, they rarely if ever...... measure O2.
So they really do not know.
And ignorance is not a good thing........


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## plantbrain (Dec 15, 2003)

tharsis said:


> hmmm...so 30 ppm should work regardless of light intensity? I figured if you are under very high light (lets say 4 x t5ho bulbs) 30 ppm of CO2 would not be enough to balance that.


No, I think some plants may use and need more.
Some, less, eg Egeria densa etc.
Erios, S belem, maybe more.


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## plantbrain (Dec 15, 2003)

The other issue is adding more O2. Few use O2 gas and it does not dissolve too easy.

O2 is also a lot more TOXIC than CO2 relatively speaking, 500% saturation would only be 4-10ppm of CO2, and this would do not harm, but 500% O2? everything would be dead as door nail.

Plants can push it to about 140%, some algae blooms etc in some systems can go to 200%, this starts toasting most things.

But if we are in the 7-11ppm range when we add CO2, then you have a pretty good flex with adding more CO2 without any issues even with sensitive fish like Full sized discus.


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## BlueJack (Apr 15, 2011)

tharsis said:


> So you are saying that you CAN increase O2 to increase the tolerable levels of CO2?


At high concentrations, CO2 limits the capacity of a fish's blood to carry oxygen and can in some cases have the same symptoms as oxygen shortage where the fish comes up to the surface to "breathe" although there is sufficient dissolved oxygen. 

Fish's gills are quite permeable to CO2....this permeability creates a situation where CO2 levels in water are not much different than CO2 levels in the fish's blood. Even if oxygen levels are at 120% you can still cause acidosis (excessive acid in the body fluids) from high CO2. 

It's not a matter of increasing O2. The blood of a fish has a great affinity for O2 and can reach 100% saturation at a relatively low dissolved oxygen content. O2 can get < 2ppm before things start getting wacky.

Once there is too much CO2 in the fish's blood, the only way to reduce it is to reduce the amount of CO2 in the water(not increase O2). Gases will always flow from a region of higher partial pressure to one of lower pressure; the larger this difference, the faster the flow.


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## tharsis (Oct 9, 2009)

plantbrain said:


> I have 60-80ppm CO2 in one tank
> 
> Respiration is both the O2 and the CO2, not just one.


Are you adding air/O2 in this tank? 



plantbrain said:


> No, I think some plants may use and need more.
> Some, less, eg Egeria densa etc.
> Erios, S belem, maybe more.


Ok, now for any given plant with a specific level of CO2 (assume 30 ppm) will increasing the light intensity lead to a situation where the plant will be CO2 limited even if 30 ppm is achieved? And if this is the case, will increasing the CO2 concentration above 30 ppm actually do anything for the plant?



plantbrain said:


> But if we are in the 7-11ppm range when we add CO2, then you have a pretty good flex with adding more CO2 without any issues even with sensitive fish like Full sized discus.


7-11 ppm O2 is pretty much saturation for the range of tank temperatures we use right? So aerating the tank to try to reach oxygen saturation between this range should give you more flexibility with the CO2?


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## kevmo911 (Sep 24, 2010)

As I assumed, folks have chimed in with views on CO2/O2 saturation. I can't comment on the relationship between fish and CO2/O2, because I have no real experience other than reading.

I stand by my my first post, however, which states that, more or less, you can try to balance CO2 and O2 as much as you want, and *it really doesn't matter* as far as our basic test results are concerned., because a fraction of a percent of any of us have access to the tools that allow us to accurately measure much of anything.

So jack your CO2 up as much as you'd like. And when you add fauna, jack it up until they freak out, and then back off a bit.

*Edit*
Just had a realization - you can change the "green zone" by changing the dKH solution to a higher level. Not something that most people would do, but definitely possible. Still vague, but there it is.


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## HD Blazingwolf (May 12, 2011)

back on page one i hhave a link to c02 test kits, 200 test for 35. also kevmo i believe all expressed the samme thing just different factors behind it. and yes i read mr barr's stuff as if im trying to get an A in science class, its also lead me to read as much as possible conncerning c02 o2 relationship as thhis is the #1 alage problem and cause of death i feel comfortable with the info i provided is not false or inaccurate.

OP its easier to try to set a maintained level of c02 (avg target on this forum seeems to be 30ppm) and control the rate of nutrient uptake with lights, too much light and u will have algae.. also comparatively its easiier to have too much light than too little try to get a stable c02 lvl and adjut ur lightinng from there.
o2- to get enough in the tank for moost of the plants and fauna you have, simple surface agitation should suffice dissolving o2 is nnext to impossible( c02 echanges 20 times easier than o2) do some research of your plants or ask questions, (about how much c02 the require) heck TINKER, play with ur levels and watch, your plants and fish are you best indicator that something is going right oor wrong.


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## plantbrain (Dec 15, 2003)

BlueJack said:


> At high concentrations, CO2 limits the capacity of a fish's blood to carry oxygen and can in some cases have the same symptoms as oxygen shortage where the fish comes up to the surface to "breathe" although there is sufficient dissolved oxygen.


How much?
And do you not agree that O2 also plays a highly dependent role with respect to O2?

Respiration is Both, it's not just one, you can kill fish with either if you push it far enough, that is NOT what is being suggested for management however.

Too much O2 is lethal
Too little O2 is lethal
Too much CO2 is lethal
Too little CO2 is NOT lethal

These are all dependent over a range.
Less O2 with less CO2 (say 4ppm O2 and .5ppm CO2) 
More CO2 with more O2 (say 30ppm CO2 and 8 ppm of O2)

Etc..........



> Fish's gills are quite permeable to CO2....this permeability creates a situation where CO2 levels in water are not much different than CO2 levels in the fish's blood. Even if oxygen levels are at 120% you can still cause acidosis (excessive acid in the body fluids) from high CO2.


Nice to say, but without knowing the CO2 concentration......and, this is not informative. 120 % for O2, you only have 1 part of the puzzle.

At what ppm of CO2 will this occur in the above example???
How much is stressful and management worthy to bother with for aquarium fish? Are species more sensitive than one another?
Which species?

We learn very little by not asking such questions.



> It's not a matter of increasing O2. The blood of a fish has a great affinity for O2 and can reach 100% saturation at a relatively low dissolved oxygen content. O2 can get < 2ppm before things start getting wacky.


I would argue that there is STRONG dependency on O2 relative to CO2.
Many will not survive (regardless of CO2) below 3-4ppm O2.
Plecos, Discus etc. 

Tell you what, knock the O2 down and see for yourself.:thumbsup:
Ever done this?

Stop circulation of the water's surface and then measure O2 with a meter. Then make a CO2 reference pH probe and use the pH/KH relationship.
You can also seal the tank some and add sugar to the filter(this will cause the O2 to drop).

Few studies have done both I've seen and few on warm water fish.



> Once there is too much CO2 in the fish's blood, the only way to reduce it is to reduce the amount of CO2 in the water(not increase O2). Gases will always flow from a region of higher partial pressure to one of lower pressure; the larger this difference, the faster the flow.


This is correct, but you are missing a larger part, the fish have a wide effective range they can tolerate and expel CO2. Is it higher when you have low vs high O2? Why not try and see for yourself?

You are suggesting that there is no dependency as far as respiration except when the O2 is less than 2ppm.

I disagree, respiration is partly expelling CO2, to which there are limits as partial pressures would predict, but it's also uptake of O2. This argument must be taken holistically.

We can also see this when circulation and higher O2 levels are used, we can add more CO2 without harm or stress to the fish(say 60ppm CO2 and 10ppm O2). Why might this be? How can I add more CO2 and not gas the fish? When I do not add more O2(say O2 at 5ppm and CO2 at 45ppm), I gas them? The hypothesis does not support the observations.

Same fish in both cases, same tank. CO2 reference cell and meter, O2 LDO meter, both calibrate and data log every 15 minutes.

I'll need a lot more convincing that there is no dependency between these two parameters:wink:

But as applied in our tanks? We only add enriched CO2 levels for maybe 6-10 hours per day, from then on, the CO2 is low.
So it takes some time to build up this CO2 in the fish and then release it. It is not chronic CO2 exposure, it is only temporary. 
This places less stress regarding CO2 removal on the fish over time vs 24/7. Some fish and tanks have little issue with 24/& CO2 though, but.....they are not breeding fish and shrimp etc either.


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## plantbrain (Dec 15, 2003)

tharsis said:


> Are you adding air/O2 in this tank?


No, not pure O2, I've done that in the past for a coupole of years to test.
Plants super saturate, this might drive to 140% O2 or about 10-11ppm relative 7ppm.



> Ok, now for any given plant with a specific level of CO2 (assume 30 ppm) will increasing the light intensity lead to a situation where the plant will be CO2 limited even if 30 ppm is achieved? And if this is the case, will increasing the CO2 concentration above 30 ppm actually do anything for the plant?


It might, I'm not sure, I have not done CO2 uptake vs light intensity curves for 300-400 species of plants:icon_redf
Do not plan on it either.

A few studies have done it for some aquatic weeds(Bowes Van Haller 1976 etc). So I do not know except for some few limited species.

I would say the levels are above 30ppm for many tanks and species and groups of mixed plants. I would be very surprised if that where NOT the case.



> 7-11 ppm O2 is pretty much saturation for the range of tank temperatures we use right? So aerating the tank to try to reach oxygen saturation between this range should give you more flexibility with the CO2?


No, 7-8 would be 100% for most aquariums, the ranges above this are due to O2 from plant growth or algae growth, colder water will have higher O2(and high CO2 or any dissolved gas)

But the plant's impact is only few hours during the middle and latter part of the day/night cycle.

From then on, it's low.


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## tharsis (Oct 9, 2009)

Thanks for the great comments everyone! Blazingwolf and Kevmo, thanks for the help, I have run my tank with fish and CO2 ~30 ppm (from an unreliable drop checker) and I have done the 'increase CO2 until the fish gasp and dial it down' method with good success in terms of plant growth. I am quite comfortable with the light CO2 relationship under 'normal operating conditions'. Currently I am inquiring about this from an academic standpoint not from a functional daily operation standpoint. I am curious about pushing it to the limit as a means of understanding the relationship. 



plantbrain said:


> Plants super saturate, this might drive to 140% O2 or about 10-11ppm relative 7ppm.
> 
> No, 7-8 would be 100% for most aquariums, the ranges above this are due to O2 from plant growth or algae growth, colder water will have higher O2(and high CO2 or any dissolved gas)
> 
> ...


To summarize; @ ~75F, 100% O2 is ~8 ppm... and supersaturation will occur when the plants/algae begin to photosynthesis as evidenced by pearling. 

So I guess this goes back to my original question:

If I keep my tank at saturation when the lights are off, it should reach supersaturation fairly early on when the lights come on (can this be qualified by observing at what point pearling occurs?). Pearling 1 hour into my photoperiod as opposed to 4-5 hours means that my tank is at supersaturation for a much longer period of time. If I can attain supersaturation early on, then theoretically I can keep higher CO2 levels...correct?

Would running an air pump through a reactor keep the tank at O2 saturation while the lights are off?


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## HD Blazingwolf (May 12, 2011)

it appears that your logic is sound. however, o2 dissolves about as well as if u dropped ur phone in the water and expected it to dissolve. unless your injecting pure o2 into a reacter i feel it would be a waste of time and energy. that being said, im just speculating. i have no idea exactly how well pure o2 will dissolve. if u have the resources. play with it and let us know what happens id love to learn something new..


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## Booger (May 17, 2004)

plantbrain said:


> No, not pure O2, I've done that in the past for a coupole of years to test.



I have been wanting to try that. Curious - what happened?


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## NJAquaBarren (Sep 16, 2009)

How about O2 and CO2 tanks and regulators feeding the same reactor? CO2 during day, O2 at night? Both during Day? 

Maybe just air pump feeding reactor? Too much air? Too little O2?

O2 tank Doesn't really seem worthwhile, but would be cool to do for a large tank


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## HD Blazingwolf (May 12, 2011)

the air you breathe is 80% nitrogen. an air pump doesnt do much good.. also ambient air is 380ppm of c02 and in home is around 750ppm. if it were sooo easy to add o2 and c02 at the same time, bubble stones would be the key for plant growth however, once c02 has been absorbed by the o2 bubbles, would it not ooff gass faster? just a thought


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## BlueJack (Apr 15, 2011)

plantbrain said:


> How much?


I wish I could give you an exact amount but I do not know this. I believe at > 20ppm utilization of oxygen begins to diminish and kidney stones can begin to develop. But I think it becomes lethal above 60ppm(prolonged exposures). Please correct me if I'm wrong. Most of our knowledge comes from articles and books we've read, not independent research. You're a lucky guy to have a job that is so closely related to your hobby. roud:

Maybe the "60ppm CO2 and 10ppm O2 without harm or stress to the fish" is the limits? (That might be the answer to your question Tharsis....about "pushing it to the limits"). Can you go higher? 




plantbrain said:


> At what ppm of CO2 will this occur in the above example???How much is stressful and management worthy to bother with for aquarium fish? Are species more sensitive than one another?
> Which species?


These are good questions for which I do not have an answer. I was hoping to describe what happens when:

"blasting CO2, and the DC is basically pee yellow 24/7....i was wondering if increasing the Oxygen would allow me to theoretically run higher CO2".

You get surface "breathing" and acidosis if levels are high enough. 



plantbrain said:


> Tell you what, knock the O2 down and see for yourself.:thumbsup: Ever done this? Is it higher when you have low vs high O2? Why not try and see for yourself?
> 
> You are suggesting that there is no dependency as far as respiration except when the O2 is less than 2ppm.


I got that 2ppm(basically lethal levels) from a study I read about carp. With 2ppm of O2 and < 10ppm CO2 all carp survived. When they kept O2 at 2ppm but increased CO2 > 10ppm, carp started to die.


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## tharsis (Oct 9, 2009)

HD Blazingwolf said:


> the air you breathe is 80% nitrogen. an air pump doesnt do much good.. also ambient air is 380ppm of c02 and in home is around 750ppm. if it were sooo easy to add o2 and c02 at the same time, bubble stones would be the key for plant growth however, once c02 has been absorbed by the o2 bubbles, would it not ooff gass faster? just a thought


But air is 20% O2 and only 0.03% CO2 so there will be much more O2 coming in contact with water than CO2 with air being passed through a reactor. An airstone does nothing for getting CO2 into the water column because it is relatively small amounts in comparison to a 100% CO2 pressurized rig. Getting 30 ppm of CO2 in the water column requires quite a bit of CO2 passing through a reactor so 0.03 % really won't cut it (even if it is 380 ppm). 

Air has a lot more O2 and the target saturation level is 8ppm, so (and this purely speculation) even with a slower dissolution rate of O2 vs CO2, the constant supply of O2 from air in a reactor should maintain fairly high levels of O2 in the water column. 

Incidentally, I hooked up an air pump to a diy intank reactor and I plan on running it until lights on tomorrow morning. I will see if it reduces the amount time for pearling to begin. I typically start to see some pearling 3-4 hours after lights on with my current set-up, so I am curious to see if I can improve on that. 

A related question to this little test - How long does it take for plants to begin photosynthesizing once the lights are turned on? Is it immediate or does it take awhile for the plants to switch over?


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## HD Blazingwolf (May 12, 2011)

you will for sure notice a difference. this has reminded me of my quest for pearling. i had a bubble stone that had 425 gph of water forced near it in my tank that help the bubbles in the water longer, pearling happened in my tank when previously did not..  take some pictures or video !!!!!!!!!!
what i've thought about since previous post is that, i believe you will have cavitation of your reactor. as the air wont dissolve quickly i believe your reactor will fill up with air readily..again.. pictures or video.. id love to see this


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## tharsis (Oct 9, 2009)

I will take some pics tomorrow, but yeah the reactor is filling up with air. I have been playing with the air flow for the last hour trying to balance the rate that the air enters. It proved to be a little difficult balancing a low enough air flow with the back pressure from the water pump. But I have it set-up where the air is very slowly accumulating in the reactor.


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## lipadj46 (Apr 6, 2011)

You can't easily hook an air pump to a reactor, its just going to fill up with air. The solution would be to get an oxygen tank and build a separate reactor for that. Now that would be cool.


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## tharsis (Oct 9, 2009)

Well I just checked my rig and the reactor filled about 1/2 way up overnight so the air was still being churned. Whether or not this has accomplished anything in terms of maintaining oxygen levels is yet to be determined as my lights don't come on for another 2.5 hours.

Here are some pics of my quick and dirty set-up:










I had to reduce the air flow enough so that it wouldn't immediately flood the reactor...to do this I connected it to these bank of valves. The cheapo valves proved to be pretty effective because even in the shutoff position they leaked just a little bit of air, reducing the total air passing into the reactor. 










I then had it passing through a T-barb (mainly because that is all that I had on hand), and into the reactor. I also controlled the flow on the water pump so that the result was essentially just a trickle of air entering into the reactor










The reactor was filled with water last night, and this is where it is this morning...not bad.










As it is now, I turned off the air pump and I am just letting it go with the air that is already in the reactor.


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## tharsis (Oct 9, 2009)

Lights went on about 1/2 hour ago, I snapped some pics of some plants:

Rotala Macrandra









Ludwigia Repens arcuata









Limnophila Aromatica









Hygro difformis









These plants usually start to show evidence of pearling about 4 hours into my photoperiod. So I will try to monitor them and see if there is an improvement on that. I have really tried to minimize the amount of air bubbles coming out of the reactor as these can attach onto plants and give the appearance of pearling.


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## HD Blazingwolf (May 12, 2011)

sweet! 

on a side note how much you charge me to ship a few of ur macrandra cliipings?? ;-)


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## tharsis (Oct 9, 2009)

I am moving to Indiana in a month so I will send you a couple clippings after I have relocated for the cost of shipping...if you can wait that long haha

i just checked the plants and the arcuata and macrandra are showing signs of pearling on the underside of the leaves. I snapped a few pics but my batteries died in the process, so I need to recharge them before I can post. The rotala rotund. is pearling away as well.


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## HD Blazingwolf (May 12, 2011)

so you are pearling before your usual start time? how exciting! also i can totally wait. however ill be bugging you in about a month


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## tharsis (Oct 9, 2009)

Yeah it is ~3 hours earlier than normal.

Here are a few pics, it is harder to see on the macrandra but you can clearly see it on the arcuata.


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## HD Blazingwolf (May 12, 2011)

very nice, ill have to setup the system i used and take pictures.. i used a fine poore bubble stone and cut the flow rate a lot and it produced tiny bubbles, when said bubbles were almost to the surface, a koralia nano 425 pushed them back aginst the glass and down. problem with the setup was since the bubbles were splayed across the front glass, it looked like a sprite tank from the front


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## Hoppy (Dec 24, 2005)

That is an interesting test, and I didn't expect the results you got.

The water surface in an aquarium is a large area "reactor" for oxygen. Compare that area to the area of any air bubbles in a tubular reactor. I would be very surprised if the reactor air had more surface area. That persuades me that just making sure the water surface is rippled over the entire surface will be the most effective reactor you can get. If you have good rippling you could about double the surface area, and the moving ripples stir up the surface air to keep fresh oxygen available to the water. Best of all, it doesn't require any replumbing, any purchase of materials, any timer, etc. It is essentially free!


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## plantbrain (Dec 15, 2003)

As suggested by Blue........if the CO2 in the fish is 100% passive and can freely move in out, regulated solely by the partial pressure, then gills function solely for O2 uptake, nothing more. 

Basically water and and plants and fish are all governed by the same passive method for entry and removal.

Not that I buy this........but if it is true, then we could EASILY design a simple method to test fish's response to CO2 toxicity.

Here's how: pH/KH test.......simply place the fish in a RO/DI water and add exactly a KH of say 2 degrees. This would make the CO2 method very accurate. Next, since as claimed.......O2 is entirely independent.......we should add say 10 fish of interest. An O2 meter can measure the O2 in situ.
All we do is slowly adjust the CO2 till we get the fish gasping, then record both O2 and CO2. To adjust O2, we can use N2 gas in place of aeration.

It would be nice if CO2 was a purely passive function in plants as well as fish, but this is not the case. It would be rather simple to measure the level at which fish LD50's occur for a wide range of species really quick with the method above, if O2 is truly independent.

But.........biological systems are often not like water alone, they fight against gradients and can adapt to compensate.

Still, it got me thinking how to test and measure CO2 toxicity and if it was true, it would be very easy to determine. All you'd need is some RO, baking soda and 10 gal tank with an air stone, pH meter and some victim fish. Researchers could measure a wide range of fish this way, yet they have not done so, which leads me to be suspect of the validity of the passive claim about CO2. Maybe I am wrong and we *can* determine it. Be an easy test.


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## plantbrain (Dec 15, 2003)

BlueJack said:


> plantbrain said:
> 
> 
> > How much? [/QOUTE]
> ...


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## tharsis (Oct 9, 2009)

Hoppy said:


> That is an interesting test, and I didn't expect the results you got.
> 
> The water surface in an aquarium is a large area "reactor" for oxygen. Compare that area to the area of any air bubbles in a tubular reactor. I would be very surprised if the reactor air had more surface area. That persuades me that just making sure the water surface is rippled over the entire surface will be the most effective reactor you can get. If you have good rippling you could about double the surface area, and the moving ripples stir up the surface air to keep fresh oxygen available to the water. Best of all, it doesn't require any replumbing, any purchase of materials, any timer, etc. It is essentially free!


I have been running the tank with very little surface agitation (it is almost a mirror) so it may be that the tank has been oxygen deprived anyways. Without any fish I didn't see the need to keep the tank aerated, plus I am still new to pressurized CO2 and the DIY CO2er in me has led me to want to preserve all the CO2 in the water 

Interesting, I may try this with alot more surface agitation and see if I can reproduce the results.

I will turn off the reactor and let things run for a day as is and see if my pearling goes back to the regular time. Then I will increase the surface agitation and see how that compares to the reactor.


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## BlueJack (Apr 15, 2011)

plantbrain said:


> As suggested by Blue........if the CO2 in the fish is 100% passive and can freely move in out, regulated solely by the partial pressure, then gills function solely for O2 uptake, nothing more.


Fish can remove CO2 through their gills. They're better at taking in oxygen (~100% effective) rather than removing CO2(~50% effective). 

http://jeb.biologists.org/content/46/2/339.full.pdf
(Sorry, not many studies are on aquarium fish...relative or not, it's still a short read.)

I also know that the difference in CO2 partial pressure of the fish's body fluid and the water is very small. Only a few torr (1 torr = 0.1333 kPa = 1316 μatm)

http://www.agu.org/pubs/crossref/2005/2004JC002564.shtml

I don't know how to reconcile these two facts. Please help

I used to think that starting at 20ppm and higher concentrations can result in acidosis, hypercapnia, sedation, or death (Summerfelt 2000). As well as reduce fish growth, decrease food conversion ratios, and reduce hematocrit and plasma chloride concentrations (Smart 1981; Danley 2001)

But since you've run tanks @ 60ppm with no ill effects, I'm not sure what is toxic or not. Is it that CO2 is not toxic but the drop in ph(of the water and the fish's blood) is what causes problems? If you can buffer your ph can run higher CO2?

I haven't read anything about the relationship of O2 to CO2, but that must be the missing link. 


Tharsis - I'm interested to see what happens with your pearling...I always think I have either too much or too little surface movement. I can't ever find a happy medium.


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## HD Blazingwolf (May 12, 2011)

I selected a few tidbits from ur article. these tidbits werent selected out of context either, just didnt feel the need to post the entire article since we have been talking about the relationship from c02 and o2



> T he ratio of diffusion coefficients for oxygen and carbon dioxide in tissues is about
> 1: 20.
> 
> An increase in venous PCOa would probably not result in an increase in dorsal
> ...


there is a relationship between o2 and c02 but not as much as i thought. o2 uptakes are fairly independent upon co2 levels, however c02 removal from the bloodstream is vastly superior than the uptake of o2 since water's solubility for c02 is much higher.

this goes back to show that high c02 is fine with conditions permitting o2 absorption from the gills, higher currents tend to reduce oxygen uptake over standing water, but also reduces the aquatic animal's need to burn energy and o2 to achieve o2 assimilation. this explains why most fishies tend to prefer some sort of flow over standing water.

all that aside, there are still toxicity levels of c02 where diffusion from the gills becomes impossible, but that would mean that the water column has (if i read correctly)between 24-35 times the amount of c02 in the fishies bloodstream (dependent upon temperature).
As most people have noticed by now, the key to aquariums plants, fish, bacteria.. etc is BALANCE.


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## HD Blazingwolf (May 12, 2011)

tharsis said:


> I have been running the tank with very little surface agitation (it is almost a mirror) so it may be that the tank has been oxygen deprived anyways. Without any fish I didn't see the need to keep the tank aerated, plus I am still new to pressurized CO2 and the DIY CO2er in me has led me to want to preserve all the CO2 in the water
> 
> Interesting, I may try this with alot more surface agitation and see if I can reproduce the results.
> 
> I will turn off the reactor and let things run for a day as is and see if my pearling goes back to the regular time. Then I will increase the surface agitation and see how that compares to the reactor.



o2 addition is vitally important even without fishies. plants need it at night to respirate, AND bacteria needs it to help maintain proper water quality


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## tharsis (Oct 9, 2009)

^ I agree and I can't imagine that my tank has been oxygen deprived as I have had a great deal of pearling over the last few weeks. The tank has been consistently above saturation for the last half of my photoperiod which I presume would be enough for the plants while the lights are out. But perhaps with little surface agitation, the O2 levels are dropping rapidly at night thus requiring additional time to reach saturation during the day. I will check the affect of simple surface agitation and compare it to my air reactor. After all this, I may just be validating the benefits of surface agitation...

Thanks for all these great links, this has turned into a very informative thread for me. Lots of good reading material


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## BlueJack (Apr 15, 2011)

HD Blazingwolf said:


> c02 removal from the bloodstream is vastly superior than the uptake of o2 since water's solubility for c02 is much higher.


I came to a different conclusion from that article. I understood it as how effective (how good or bad) gills are at uptake/removal of O2/CO2. Findings were, that gills are pretty good at taking in O2(~100% effective) and half as good at removing CO2 (~50% effective)












HD Blazingwolf said:


> all that aside, there are still toxicity levels of c02 where diffusion from the gills becomes impossible, but that would mean that the water column has (if i read correctly)between 24-35 times the amount of c02 in the fishies bloodstream (dependent upon temperature).


I might be wrong here, but I think that's just the solubility ratio of O2/CO2, not the toxicity levels. For every 1 part O2 that dissolves in water there will be 24-35(depending on temp) parts of CO2 in water.

The part that I'm having trouble reconciling is:

Since, fish can regulate the amount of CO2 inside them (I'm assuming by just breathing more/faster to expel the CO2 quicker. This is probably why fish gasp or surface breathe). Then why is the CO2 partial pressure inside the fish, the same as in the water. (i.e., 45 ppm CO2 in water = ~45 ppm CO2 inside fish). They should be able to regulate themselves out of trouble, right?

Also, since Mr. Barr runs tanks at 60-80ppm without casualties, what are toxic levels? Is the relationship more complex than just CO2? Is it the ratio of O2 :CO2 that's really important? Start at no lower than 4ppm O2 and increase up to 10ppm O2 as CO2 is increased? What proportions should be used?


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## HD Blazingwolf (May 12, 2011)

i stand corrected, i re read the article. you are right that is the solubility of c02 and o2 respectively. If i were to make a hunch toxicity would be higher than the solubility ratios.
if there is 1 o2 for ever 24 c02 then toxicity would be 1 o2 for every 25 and up c02. that's what im basing my hunch on at this point and i will try to test that since i now have a fishless tank (son liked needle valve). 
gills can transfer c02 at 50% efficiency, BUT, the solubility of the water is 20 times higher than o2. is the efficiency based solely on gill function? or is it compared to solubility of c02 in water? 
does that mean its 20 times more effective x 50%? = 10 times more effective? or can the fish transfer half that c02 its body is producing?


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## BlueJack (Apr 15, 2011)

HD Blazingwolf said:


> gills can transfer c02 at 50% efficiency, BUT, the solubility of the water is 20 times higher than o2. is the efficiency based solely on gill function? or is it compared to solubility of c02 in water?


I'm assuming it's both. They don't say but I assume they did the test under low levels of dissolved CO2(so that CO2 readily dissolves in water), and came out with ~50% efficiency. What happens in levels of higher CO2 45,60,80,100ppm I do not know. What is the upper limit where CO2 stops dissolving in water? I would guess that it does effect efficiency. In the article it mentions low O2 has a great impact on the efficiency of gills to extract O2. It's a double whammy for the fish...not only is there less O2 but it's gills work much less efficiently on top of that.



HD Blazingwolf said:


> does that mean its 20 times more effective x 50%? = 10 times more effective? or can the fish transfer half that c02 its body is producing?


I think fish can transfer more than that. 50% through the gills and "I know fish can diffuse CO2 through their skin/bodies"(Barr). How much I'm not sure.


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## HD Blazingwolf (May 12, 2011)

WOW i wish i had the money to invest in test equipment that i dont even know how to use yet. i've thought about this all day.. 
another interesting piece of the puzzle. Humans create bicarbonates to transfer c02 from the cell to the blood vessels where once it passes through the membrane into the lungs it is transferred back to c02, we lose ions in the process as an exchange for saving water. I wonder how bicarbonates play a role in fish respiration?


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## Hoppy (Dec 24, 2005)

BlueJack said:


> Also, since Mr. Barr runs tanks at 60-80ppm without casualties, what are toxic levels? Is the relationship more complex than just CO2? Is it the ratio of O2 :CO2 that's really important? Start at no lower than 4ppm O2 and increase up to 10ppm O2 as CO2 is increased? What proportions should be used?


Keep in mind that Tom uses a precision CO2 probe to measure the amount of CO2 in his tank water, something none of us have. That means his 60-80 ppm might be seen as 20-30 by some of us, and 150-200 by others of us. None of the rest of us can measure CO2 with any accuracy at all.


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## HD Blazingwolf (May 12, 2011)

Hoppy said:


> Keep in mind that Tom uses a precision CO2 probe to measure the amount of CO2 in his tank water, something none of us have. That means his 60-80 ppm might be seen as 20-30 by some of us, and 150-200 by others of us. None of the rest of us can measure CO2 with any accuracy at all.


NOT as accurate as a probe im sure BUT
TEST KIT http://www.fondriest.com/products/hach_143601.htm (200 tests 35 bux)

it has a +/- 5 % accuracy rating so if you say tested and had 100 ppm c02 you could be between 95-105 ppm.. MUCH closer than any drop checker or chart could ever provide AND at a reasonable cost for those interested in testing c02 levels


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## Hoppy (Dec 24, 2005)

I don't believe that Hach kit is significantly more accurate than the KH/pH method. It appears to be a similar test, one that works best if there is nothing else in the water that affects pH except carbonates and CO2. The indicator solution is an acid/base indicator, and they titrate with sodium hydroxide solution, slowly increasing the pH of the mixture until it goes from acid to base.


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## BlueJack (Apr 15, 2011)

Hoppy -

How far off is the 4dkh drop checker method?

0-19ppm are blue shades
19-47ppm are green shades (perfect green being 30ppm)
47+ppm are yellow shades

How far off are those? Just curious.


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## tharsis (Oct 9, 2009)

Interesting convo going on here  I can't contribute much to the ideas but I am loving the dialogue. It is always nice to have exchange of ideas with references. 

I think you may be able to get a bit more accurate results at higher ppm in the drop checker if you use a higher dkh solution. 

As for my little tests:

I tried the tank without my rig and I ended up seeing pearling at ~3:30 so a full 2.5 hours later than with the reactor. I took it out and now have a koralia 4 (1200 gph) blasting up to the surface, enough surface agitation to make a reefer blush. 

I will see how this compares tomorrow. I Wish I had an O2 and CO2 probe


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## BlueJack (Apr 15, 2011)

tharsis said:


> I think you may be able to get a bit more accurate results at higher ppm in the drop checker if you use a higher dkh solution.


The numbers just move up a little.

With 5dkh-
0-24ppm Blueish
24-60ppm Greenish (perfect green 38)
60+ppm yellowish

With 6dkh-
0-28ppm blueish
28-71ppm greenish (perfect green 45)
71+ppm yellowish

With 10dkh-
0-47ppm blueish
47-119ppm greenish (perfect green 75)
119+ppm yellowish 

etc...

I'm getting these numbers from a drop checker calculator.

http://co2.petalphile.com/


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## HD Blazingwolf (May 12, 2011)

tharsis what size tank do u have? and how is the koralia positioned? mine is a nano 425 on the back wall facing up and over ill get a pic up in a few minutes, provides decent agitation. not as much as id like but it helps keep a nice flow in the tank as well


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## tharsis (Oct 9, 2009)

its a 75 gallon, I have it on the left side wall near the back pointing up and towards the front right corner. It is too much flow for the long term but i wanted to go with a crazy amount of surface agitation at first. Next I will try it with just a gentle surface ripple. 

I will post pics later.


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## Hoppy (Dec 24, 2005)

BlueJack said:


> Hoppy -
> 
> How far off is the 4dkh drop checker method?
> 
> ...


A drop checker reacts slowly to changes in CO2 concentration, so unless the concentration remains the same for a few hours a drop checker is always catching up. And, judging the color of the fluid is very difficult for some or most people - we don't all have equal color perception. Those two factors make it always just a rough guide, good for making sure you are working in the 20+ ppm range and not the 5+ range. The fish will tell you if you have too much.


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## tharsis (Oct 9, 2009)

^ I am guessing that the design of the drop checker will have a large influence on the reaction time. A smaller volume of liquid will respond much quicker won't it? 


Here are a couple crummy pics of the surface agitation. The agitation is actually quite a bit more than these pics suggest, but you get the idea.


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## HD Blazingwolf (May 12, 2011)

mine and yes those swirls are the bubbles left from my cerge reactor. 
this is on a 29 gallon.
also a phone pic. the plants arent actually yellow looking. it looks great in the camera until it takes the pic


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## tharsis (Oct 9, 2009)

hmmm so it is past 3:30 and I am still not getting any pearling from my plants with just the surface agitation. 

I did a water change yesterday so I am wondering if that lowered the O2 levels in the tank, it is odd that I haven't reached saturation yet. I think I will keep running the koralia for another night and check again tomorrow.

Is it possible to have too much agitation? Can you degass O2 as well with surface agitation? Not sure if you can reach a point where the rate of outgassing exceeds the rate of dissolution.

EDIT: It is now 5:00 and still no pearling...wondering if maybe the strong current is blowing the bubbles off of the leaves before they can accumulate.


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## HD Blazingwolf (May 12, 2011)

that does make a difference. if i turn my koralia off i have a better chance of pearling because the water around the plants gets saturated but after a few days i notice that they are becomming nutrient deficient so its necessary in my tank to have it so all the plants get the things they need


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## Hoppy (Dec 24, 2005)

It takes more than high O2 content to get pearling. The plants also have to be growing fast enough to generate enough O2 to form bubbles. A better test is to keep the ppm of CO2 roughly constant and run with then without the surface rippling. You will need a higher bubble rate with the rippling to make up for the added loss of CO2 from the surface.

Both of those photos above show what I consider to be good surface rippling. Tom Barr's tanks have a comparable amount of rippling, as did I when I was running higher light and pressurized CO2.


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## HD Blazingwolf (May 12, 2011)

also, since i have an empty tank im playing with c02, my tank is kept at 45ppm c02 avg, ive raised c02 lvls and my cabomba, ludwigia repens broadleaf, and wisteria pearl when they didnt at 45ppm. this iis as of 4 hours ago. 
hoppy my surface agitation is at an all time low, i favor high rippling in my tank, i like the wavey light effect and of course the sound


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## tharsis (Oct 9, 2009)

Hoppy said:


> It takes more than high O2 content to get pearling. The plants also have to be growing fast enough to generate enough O2 to form bubbles. A better test is to keep the ppm of CO2 roughly constant and run with then without the surface rippling. You will need a higher bubble rate with the rippling to make up for the added loss of CO2 from the surface.
> 
> Both of those photos above show what I consider to be good surface rippling. Tom Barr's tanks have a comparable amount of rippling, as did I when I was running higher light and pressurized CO2.


My rationale is that with the O2 at saturation in the tank, any O2 formed through photosynthesis will appear in the form of pearling. 

Are you suggesting that i am not seeing pearling because my plants are not photosynthesizing as much due to a CO2 limitation from the additional surface agitation? 

If that is the case then I can see an automatic benefit from using an air reactor as opposed to excessive surface rippling. I can maintain O2 saturation and use much less CO2 to attain the same level of photosynthesis in my plants.


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## tharsis (Oct 9, 2009)

Well it looks like I have been able to keep my water close to oxygen saturation over the last week just with air. I decided to do away with my in tank rig and I just hooked up an air pump to my cerges reactor. 

Every evening, ~30 minutes prior to lights out, I connect the air pump to the reactor and let it fill up. By lights on the following day, all the air has dissipated from the reactor. I have been observing pearling at about an hour into my photoperiod suggesting that saturation is maintained.


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