# Continuous CO2 Injection



## Robert42 (Aug 16, 2017)

I have just read an article by Karen Randall. "Carbon Dioxide in Planted Freshwater Aquaria". I looked Karren up and she seems to be a very highly regarded aquarist. So I was very surprised to read, "_In a properly buffered tank that is not overstocked, however, most people find that the oxygen level in the tank remains high enough, and the pH in the tank remains more stable, if the CO2 is left to run day and night without the interference of nighttime aeration._"
In my experience, it takes my CO2 levels about 3 hours to go green in the drop checker. It will then gradually creep up.
Is anyone using continuous CO2? I can see the rationale that Karren points out in that it gives a more stable pH to the tank.
So I am in a quandary as to give this a go.


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## cozzuol (Feb 26, 2008)

I am using a pH controller linked to the CO2 solenoid valve. It only stops the injection when pH is below 6.7, otherwise, it is continuous. No problems up to now...


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## Robert42 (Aug 16, 2017)

cozzuol said:


> I am using a pH controller linked to the CO2 solenoid valve. It only stops the injection when pH is below 6.7, otherwise, it is continuous. No problems up to now...


Thanks for your reply. I have not considered using a pH Controler. I would like to hear from anyone just running the CO2 overnight as well as the day.


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## RxSub (Feb 25, 2018)

I am running Co2 24/7 with no issues. As my lights are in the medium PAR scale, have enough with 1,5 bps in a 30 gal. The surface skimmer provides enough surface agitation though.

(excuse my english, it's not the best)

Enviado desde mi SM-G900F mediante Tapatalk


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## madcrafted (Dec 23, 2017)

I see no problems doing this. Did it myself for a few weeks to help grow in some mosses in a shrimp tank. I set flow to drop pH by .5, which yielded about 15 ppm continuously. It helped speed things up. Most people that run DIY CO2 run it 24/7 without issue. As long as there is sufficient agitation to keep O2 levels up, you could push higher levels than I did. I was being cautious with sensitive shrimps.


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## Edward (Apr 11, 2005)

All my aquariums run CO2 and *aeration* 24/7, works also with 400 PAR lights.
There are number of reasons, water pH is lower and more stable, CO2 concentration is more consistent, plants can take nutrients 24/7, trace element chelating is more stable, trace element bioavailability is better, more ammonium than harmful ammonia, less equipment to worry about, …


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## Seattle_Aquarist (Jun 15, 2008)

Hi @Robert42,

Yes, Karen Randall is a highly respected and active aquarist, plant explorer (with Christel Kasselmann), aquascape judge, and on the Board or Directors for the Aquatic Gardener's Association (AGA). I run all of my tanks 24/7 with about 30ppm of CO2.


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## Deanna (Feb 15, 2017)

I've run it both ways and have never observed any difference so, I figured just do it when the lights are on so I run to the CO2 store every 4 months instead of every two months. As long as your gas exchange is good, especially at night, the fish and plants will be happy.


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## jeffkrol (Jun 5, 2013)

Seattle_Aquarist said:


> Hi @*Robert42*,
> 
> Yes, Karen Randall is a highly respected and active aquarist, plant explorer (with Christal Kasselmann), aquascape judge, and on the Board or Directors for the Aquatic Gardener's Association (AGA). I run all of my tanks 24/7 with about 30ppm of CO2.


Actually just want to see data proving things one way or another..
pH meters will not stop a drop in pH past the set point.
question is does nightly "natural" CO2 still decrease pH and if so by how much ect..
Keep in mind one of her qualifications is.."a well buffered aquarium"..though from the below that is most tanks (any above 1dkh).


> Myth: A Low KH results in a larger pH swing when adding CO2.
> Many people are under the mistaken impression that a low KH results in large pH swings when adding CO2, while raising the KH will result in smaller pH swings. This is not the case. The KH will move the start and end pH values, but the pH swing will be the same for a given level of CO2. (note breaks down around 1dkh)





> The RATE of CO2 is what you really want to know, not a pH.
> Say the tank used 50mls /300 seconds of CO2 gas.
> This is entirely independent of pH/KH/Tannins, any other wonky stuff in the water that throws the pH/KH/CO2 chart off.


sorry just a reminder. Found it while looking for numbers..
http://www.plantedtank.net/forums/1...524953-co2-lets-finalize-ph-meter-kh-ppm.html

Don't think it hurts either way as long as surface exchange is steady..just want real data..

Just not sure how "steady" it is though instinct tells me the swing will normally be less than off at night/on in day.........so there is that.

On a side note.. She really doesn't like non-Excel glut..

anyone want to stay up all night a record readings???


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## dukydaf (Dec 27, 2004)

There is no need to run CO2 at night, plants will not use it when lights are off. Tried it, no effect. Plants and fish regulate their internal pH any way so no use in keeping it stable, how stable is stable ? Not all nutrients benefit from low pH.

If you really want to keep your CO2 stable, remove all potential acid/alkaline leaching sources and get a PH controller. It may not stop the pH from going below the set point but it will stop CO2 injection when the pH drops below that. If you do not have a massive acid source or CO2 bubble this will stop the pH from going down pretty soon. 

Without a pH controller you have to get extreme degassing and very high CO2 input for a stable pH. Degas enough so that plant use during the day is very small compared to your degassed amount, add enough CO2 so you get 30ppm despite the extreme degassing. 

Using any of the above you will you your tank about 3x as fast. Add to this that large tank have great inertia and will not fully degas by the next day anyway. So if the drop from atmospheric equilibrium(so called "degassed") pH is 1 at lights off, you will likely get a 0.5 increase by the next day with decent aeration. So overall you have a 0.5 daily swing and no plant benefit. Worth the 3x consumption ?

I would not do it for the reasons given in the article. Fish and plants experience pH change all the time in their habitat. Lakes behave like our aquariums and get even more stratified. River water will vary greatly depending on how much rain is received upstream.

Also, many of the things in the article were debunked about 15 years ago in the hobby or just wrong. Interesting to see that AGA is proud of such an article. Speaks volumes. So I question the premise of the change. Some examples of what I am speaking about: 



> In the absence of CO2, many plants have the ability to meet their carbon needs by splitting carbon
> directly from carbonates in the water, which is the second method.


Actually it is a minority of the current plants in the hobby, mostly those obligate aquatic plants. 



> The amount of CO2 needed in the aquarium for good plant growth is considered to be around 15 milligrams per liter (mg/L),


Most sources and plant growers go for 30 and above , but glad to see her using the correct units mg/L not ppm.



> Room air contains 1 to 3 mg/L of CO2, and aerated water dissolves only 0.7 the CO2 content of the air.


Thankfully for all terrestrial plants, air contains somewhere between 350-407mg/L, just 100x more nothing major. 



> In fact, the proper use of supplemental CO2 with appropriate lighting and trace element supplementation should actually increase the levels of dissolved oxygen in the water.


We have CO2, light and trace elements. Where are the macro nutrients ? Pretty sure the O2 levels will not increase without them. Oh wait here they are: 



> If the two major nutrients in the tank (nitrogen products and phosphate) are increased beyond the needs of the plants, you will experience algae problems.


Man, see told you non-limiting nutrients are a lie. Tom Barr's aquariums are full of algae with all that PO4 sitting there in water. 



> However, if the water is not properly buffered, or if too much CO2 is introduced, the pH in the tank can drop quickly to levels that are lethal to fish.


Oh, pH levels and fish... Pretty sure it is the CO2 that kills them at that point. In normal aquariums, even with low KH you will not need to go lower than pH 5 with CO2 injection. If you do, you added to many other acids to the tank. Plenty of counter examples here as well of people with low KH, CO2 injection and good plant growth. 



> Those aquarists with very soft water must increase the alkalinity of their water. Without the buffering properties of KH, CO2 supplementation can cause the pH to plummet, to the detriment of plants and, more especially, the fish.


Now it seems it is a must, it does not matter that in the aquarium are some fish and shrimps which need low KH. And plants seem to also be affected by low pH. Let's see... no _Vallisneria _still grows at a pH below 6, _Egeria _as well... other high pH plants in mind ?



> The goal should be to find a rate of CO2 supplementation that falls within this range, and produces a pH reading that is neutral (7.0) or slightly below


So if the water already has a pH of 7 or slightly below, the CO2 goal was achieved ??? Or if it is above 7 but fish are gasping ? 
Think a better goal would be to add enough CO2 to cover the requirements of your plants under the supplied amount of light. If this is too much to keep fish alive, reduce the light intensity.


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## Edward (Apr 11, 2005)

dukydaf said:


> There is no need to run CO2 at night, plants will not use it when lights are off.


 Do you know of any evidence about plants not taking or using nutrients at night?


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## OVT (Nov 29, 2011)

The article indeed leaves a lot to be desired: too many absolutes and factual errors do not help author's credibility.

For me, the risks of running co2 24/7 outweight the benefits. I had too many equipment failures and plain stupidity on my part that resulted in tankfulls of dead fish.

Some of my incidents:
- over filling the tank in the evening, resulting in surface agitation change
- air wand getting clogged over time
- air tubing popping off the air pump
- air pump filter getting clogged with dust
- obstructing the air pump intake by leaving it on a wet paper towel
- running co2 at max and getting EOTD at 3 am

All avoidable and preventable for sure. I just don't trust myself without adult supervision.


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## jeffkrol (Jun 5, 2013)

Edward said:


> Do you know of any evidence about plants not taking or using nutrients at night?


Depends what nutrients you are referring to. 
Last I knew (decades ago) plants do most of their real growth at night. 
During the day most "growth" is just expansion of existing cells. 

As to the nutrient CO2 no I suspect very little use.
Photosynthesis doesn't "stop" except at low enough light levels that zero photons are "caught"..
Conversely plant respiration (release of energy to build stuff) is continuous but increases at night due to no longer needing this energy for anything related to photosynthesis.

This is kind of fun and puts a few concepts in perspective..
https://www.quora.com/Do-plants-grow-at-night



> Plants have a mission: Catch the sunlight, convert and store the energy when you can. Grow later. During photosynthesis the plants grab all the light, carbon dioxide and water passible. With those ingredients that plant makes sugars, starches and other vital compounds.
> What about plant GROWTH? Not yet. Make FOOD while the sun shines. Save cell division and elongation(growth) for the night shift.





> Indeed, plant behavior is tightly controlled by the sun. During the day, plants soak up sunlight during photosynthesis, the process they use to get energy. But when the sun goes down, plants’ opportunity to eat disappears and other physiological processes take over, including energy metabolism and growth.
> Personal note, mostly related to terrestrial plants: Plant uptake of water during the day can "swell" cells so you get "growth" but not real growth (increase in cells).
> Daylight increases biomass by the simple accumulation of sugars.. not by adding complex structures. All simplistic of course.


Though as you can see from above.. some things are made..



> Confuse your friends… Everyone knows that plants grow towards the light, right? Actually they don’t. The light side of the plant grows SLOWER while the dark side of the plant grows FASTER……So they are growing AWAY from the dark!


for fun.. Results are the same..

Leaving out circadian rhythms for now..

Doesn't really answer the question because it depends on which nutrients and what they are used for..
some are used in the day some at night more, some both..


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## Deanna (Feb 15, 2017)

@jeffkrol: You just shook-up my traditional thinking! My memories instantly turned to the commonly reported comments, by farmers, that they can hear the corn growing on calm nights, as the leaves move against each other. Of course, those are terrestrial plants - if that matters.

It does seem to be more an issue of circadian rhythms. One interesting comment, in one of the articles:


> Plants forced on a light cycle 12 hours out of phase didn’t do this and were thus chewed up.


which was referring to the ability of plants to put up defenses against attackers.

Hmmm …could that apply to algae formation on leaves, bringing in the whole allelopathy issue? However, another article (embedded in the UKAPS thread), claims that we can force a new circadian rhythm.

Here is what a quick Googling found:

ucsdnews.ucsd.edu/archive/newsrel/science/2011_07evening-complex.asp
https://www.popsci.com/blog-network/our-modern-plagues/do-plants-sleep
https://www.ukaps.org/forum/threads/do-plants-grow-faster-at-night.39891/

Biologists: correct me if I’m about to be wrong.

What do plants use to create mass? Carbon or, more correctly, sugar (cellulose and starch) made from carbon (CO2) by photosynthesis or respiration (‘burning’ O2). As I recall, they are always consuming carbon (CO2) and giving off the waste gas (O2) - day and night, but need more O2 at night. At night, O2 consumption increases because they now have to rely upon energy from ‘burning’ O2 to grow (Calvin cycle), rather than using energy from photosynthesis. Thus, the need to be sure there is plentiful O2 at night. This is respiration, which is the opposite of photosynthesis, when plants use O2 to make the sugars from the carbon rather than using light to do it but, I guess, they still use the same amount of CO2 – maybe even more just before whatever circadian rhythm “dawn” we artificially create.

This may make a case to have CO2 available all the time or, at least, come on a lot earlier than just in time to meet ‘lights on’. Would it be better to make sure that plants have access to the carbon when their growth is actually at it’s peak (before “dawn”)? An interesting experiment, which I will try in the near future, would be to run CO2 at night and turn it off during the day.


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## jeffkrol (Jun 5, 2013)

Which mass?.. Cell walls are mostly complex carbohydrates which are for the most part simple sugar molecules chained together.
Plants mostly gains mass (ignoring mineral uptake for the moment) by building sugars from water and CO2. Assembly is driven (energy collected and turned to a usable form) by collecting light energy. Respiration also contributes.
We build mass by consuming mass.. and changing it. Which requires energy from respiration.



> In the primary (growing) plant cell wall, the major carbohydrates are cellulose, hemicellulose and pectin.


Proteins are built w/ amino acids so need carbon, nitrogen, sulfur ect.










Oh and chlorophyll need Mg.. It is closely related to hemoglobin w/ the main difference hemoglobin uses Iron

All "assembly" requires energy..supplied both in the photosynthesis reaction chain and respiration..

Easiest to think of this as many conveyor belts, each requiring parts and energy to start and assemble..
Which belts are moving and at what speed and what energy the assembly "people" have is determined by input and product availability.
A "supervisor" (regulatory hormones) walks around and turns some on, slows or speeds some up, or shuts some down.
Supervisors themselves are assembled somewhere based on conditions.

Carbon comes from sugars created in photosynthesis.
These "parts" are assembled into chains or split for energy.

AFAICT if no light CO2 is unnecessary since the conveyor belt that uses it is shut down.
But there is now a pile of parts for others..hopefully.

algae germinates w/ free ammonia..and doubt, though not impossible, that circ. rhythms play much of an impact.. 
Plant would need to produce "algaecides" based on periodicity..which is ?? to me.

Of course the complication (it's always complicated) is each "belt" can have dependencies on other belts..


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## Deanna (Feb 15, 2017)

Mass as in "mostly" and then just the dry mass. The conveyor belts are the processes. What is coming out at the end of the assembly line? It's a product made mostly of water, but the dry mass is mostly carbon.


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## jeffkrol (Jun 5, 2013)

Proteins, complex carbohydrates enzymes .. Everything not sugar.. 
All starting w/ photosynthesis (maj production is "bricks" so to speak.). splitting H2O and CO2 using sunlight and chemicals from other conveyor belts. and re-assembling it into sugar and "discarding"
(for the time being) Oxygen.












almost all plant mass (except starter packet.. i.e seed and adsorbed minerals ) is built w/ the mass created by splitting water and CO2.
ATP and NADPH is the "fuel" 

ONLY water and CO2 is needed to make glucose..and the water is err destroyed..
Think of sugar.. you can't boil off water it's gone.. well sugar will probably pick some water up from the air but that doesn't count.


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## Deanna (Feb 15, 2017)

No argument about the process. It's the result of all that: carbon and water = bulk of plant we see.

More interesting is the amount of growth that may or may not occur at night, when in the night and if adding CO2 would help with that.


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## jeffkrol (Jun 5, 2013)

Deanna said:


> No argument about the process. It's the result of all that: carbon and water = bulk of plant we see.
> 
> More interesting is the amount of growth that may or may not occur at night, when in the night and if adding CO2 would help with that.


Adding CO2 at night will not contribute to growth. Plants are expelling it..
pH stability is the only possible use.


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## Deanna (Feb 15, 2017)

While respiring, they are growing. Nighttime growth, then, must all be from the stored sugars.

If plants experience a growth spurt, before dawn, using up the stored sugars, the next question is: how much light defines "dawn"? for example, if I have my lights come on at 10AM, I start the CO2 flowing at 8AM. However, there is plenty of ambient light, from natural sunlight, in the room well before 8AM. So, if the plants start photosynthesizing with this ambient light (as I suspect they do), then we really need to turn the CO2 on before true dawn, not in coordination with aquarium "lights on." Perhaps this is why leaving CO2 on all night provides any, if measurable, benefit.


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## Edward (Apr 11, 2005)

The goal is to offer plants enough nutrients day and night so they can store it and be ready for the next light period. Turning CO2 at night off allows pH go up making precious Fe, Mn Zn and Cu bioavailability go down. Also, it lowers chelating ability to protect these essential nutrients from becoming non-bioavailable. They become oxidized, unusable and insoluble part of substrate. No water change can then remove them. Plants and fauna will do better not because of CO2 addition at night but because of the pH affect it has. 

I would like to add, even without aeration fish don’t die when the CO2 addition is proper. The aeration is essential with or without CO2.


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## Maryland Guppy (Dec 6, 2014)

No one that I recall has mentioned how plants typically close up @ lights out.
Lunar cycle on moonlights has to be dim enough on full moon so the plants don't think it's time to grow again.

Had this problem due to the number of pucks over the tank.


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## Deanna (Feb 15, 2017)

Maryland Guppy said:


> No one that I recall has mentioned how plants typically close up @ lights out.
> Lunar cycle on moonlights has to be dim enough on full moon so the plants don't think it's time to grow again.
> 
> Had this problem due to the number of pucks over the tank.


I've found various studies that state that the dim blue light of dawn is the critical light that awakens the photosynthesis mechanism, preparing the plant to receive full spectrum later (won't post them because I can't affirm their credibility). Basically, the consensus is that the blue light triggers the stomata (guard cell) to open, allowing potassium to enter and this morning cup of coffee now gets things moving. Hard to tell, from the studies, if there is enough ambient blue light in a room, during the dawn hours, to trigger this. So, it may be better to awaken our plants slowly with an hour or so of blue-only light.

When light fades, the stomata (guard cell) closes up, ending photosynthesis, and respiration can begin. Perhaps a sudden shutting off of light would have no negative effect since the stomata would simply close, unless the respiration process needs time to start up. I saw no info regarding how much PAR it takes to open or keep open the stomata, but references to very little blue light being enough were repeated. It may be that moon lights do provide enough blue light to keep the stomata open. This is conjecture on my part.


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## jeffkrol (Jun 5, 2013)

Aquatic plants lack stomata..or severely reduced..
Stomata and waxy cuticles are for water retention.. and yes gas exchange..but does not apply well to aquatics.
Thus they dry rapidly out of water (no control) and need to change leaves in the case of plants going from emergent to submerged state.


> In aquatic plants, the epidermis is not protective but absorbs gases and nutrients directly from the water. The epidermis in the typical hydrophyte has an extremely thin cuticle, and the thin cellulose walls permit ready absorption from the surrounding water.
> 
> Commonly the chloroplasts are found in epidermal cells of leaves, especially when the leaves are very thin; these chloroplasts utilize the weak light under water for photosynthesis. In submerged plant, stomata are not present, and exchange of gases takes place directly through cell walls. The floating leaves of aquatic plants have abundant stomata on the upper surface.


http://www.biologydiscussion.com/botany/ecological-anatomy-with-diagrams-botany/20610










Respiration is virtually continuous. Only difference is if it's more heavily contributing energy to photosynthesis or building cells..

Light compensation point varies by species and types. most aquatics are sort of low light plants so point is quite low.


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## Deanna (Feb 15, 2017)

jeffkrol said:


> Aquatic plants lack stomata..or severely reduced..
> Stomata and waxy cuticles are for water retention.. and yes gas exchange..but does not apply well to aquatics.
> Thus they dry rapidly out of water (no control) and need to change leaves in the case of plants going from emergent to submerged state.
> 
> ...


Thanks for correcting. Further Googling indicates that the early blue light triggers photosynthesis in aquatic plants as soon as the light appears. The light compensation point seems to be very low, but does vary by species. Perhaps because there is no guard (stomata) to act as gatekeeper. I suppose that means that CO2 will need to be started before dawn to be ready for even the little ambient light that does appear in a room. Moon lights may still not be a good thing.

I did run across an interesting phenomena that supports aquatic plants using CO2 in the dark. It's called "CAM photosynthesis." Apparently, many aquatic plants (like some terrestrial plants) have adapted to competition for scarce CO2 during the day by waiting until the darkness. When other plants stop consuming CO2, they begin/continue consuming CO2.



> CAM photosynthesis is also found in aquatic species in at least 4 genera, including: Isoetes, Crassula, Littorella, Sagittaria, and possibly Vallisneria


Perhaps for those species, and maybe others, CO2 at night would be beneficial.

Any further insight is welcome.


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## OVT (Nov 29, 2011)

The above would suggest that photosynthesis and growth are not mutually exclusive but overlapping processes for aquatic plants. Does the same hold true for various algae? Throw in floaters and moonlights into the mix and algae might be at a disadvantage during the lights out.


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## jeffkrol (Jun 5, 2013)

Deanna said:


> Thanks for correcting. Further Googling indicates that the early blue light triggers photosynthesis in aquatic plants as soon as the light appears. The light compensation point seems to be very low, but does vary by species. Perhaps because there is no guard (stomata) to act as gatekeeper. I suppose that means that CO2 will need to be started before dawn to be ready for even the little ambient light that does appear in a room. Moon lights may still not be a good thing.
> 
> I did run across an interesting phenomena that supports aquatic plants using CO2 in the dark. It's called "CAM photosynthesis." Apparently, many aquatic plants (like some terrestrial plants) have adapted to competition for scarce CO2 during the day by waiting until the darkness. When other plants stop consuming CO2, they begin/continue consuming CO2.
> 
> ...


Aquatic plants store excess gas naturally.. See article posted earlier..Though at lights out, probably mostly O2
and don't forget that respiration produces CO2. Between the plants/fish/bacteria respiring at night, can't see CO2 being in short supply.

Thanks though, been a while since I've considered the "other" reactions..


> In contrast, CO2 builds up to several times air-equilibrium during the night when respiration processes dominates. Under these environmental conditions, plants with CAM photosynthesis may maintain positive underwater net photosynthesis also during times when the external CO2 concentration drops to sub air-equilibrium values. However, CAM photosynthesis may also restrict photorespiration which is often high in aquatic plants as a consequence of the slow gas diffusion in water compared to in air; CO2 is only slowly replenished at the site of Rubisco. In addition, O2 tends to build up in the tissue because of the lower solubility of O2 compared to CO2. CAM activity in the present study was indicated by 9.7-fold higher leaf malate at dawn, compared with at dusk, and CAM activity was confirmed also as changes in titratable acidity (μmol H+ equivalents) of leaves. Leaves high in malate not only showed higher underwater net photosynthesis at low external CO2 but also less apparent photorespiration. Suppression by CAM of apparent photorespiration was evident at a range of O2 concentrations, including values below air equilibrium. At high O2 of 2.2-fold atmospheric equilibrium, net photosynthesis was reduced substantially and although it remained positive in leaves containing high malate, became negative in those low in malate. In situ measurements of internal leaf O2 concentrations in Isoëtes australis, an Australian aquatic CAM plant inhabiting granite rock pools, showed that late afternoon O2 increased to 32 kPa in the leaf lacunae while dropping to below 1 kPa during the night. It is thus suggested that CAM in aquatic plants enables higher rates of underwater net photosynthesis over large O2 and CO2 concentration ranges in floodwaters, via increased CO2 fixation and suppression of photorespiration.


so it's possible "dark" CO2 injection can increase photosynthesis.
Question is .. How much would it effect it?

Injected tanks will have a fairly large "over atmosphere" concentration of CO2.



> . In contrast, CO2 builds up to several times air-equilibrium during the night when respiration processes dominates. Under these environmental conditions, plants with CAM photosynthesis may maintain positive underwater net photosynthesis also during times when the external CO2 concentration drops to sub air-equilibrium values


http://www.is-pa.org/IBC 2011 Ole_Pedersen.html

This sort of opens up another parallel discussion on if O2 levels can be "too much".. 


> This weakness in the enzyme is the cause of photorespiration, such that healthy leaves in bright light may have zero net carbon fixation when the ratio of O
> 2 to CO2 reaches a threshold at which oxygen is fixed instead of carbon.





> The double-carbon fixation pathway confers a greater photosynthetic efficiency on C4 plants over C3 plants, because the C3 enzyme Rubisco is highly inefficient in the presence of elevated levels of oxygen. In order for the enzyme to operate, carbon dioxide must first attach to the enzyme at a particular location known as the active site.
> 
> However, oxygen is also able to attach to this active site and prevent carbon dioxide from attaching, a process known as photorespiration. As a consequence, there is an ongoing competition between these two gases for attachment at the active site of the Rubisco enzyme. Not only does the oxygen outcompete carbon dioxide; when oxygen binds to Rubisco, it also destroys some of the molecules in the Calvin
> cycle.


http://lifeofplant.blogspot.com/2011/10/c4-and-cam-photosynthesis.html

Third area.. IF you run known CAM aquatic plants why inject CO2 in daylight.. 


> Consequently, pools of water may be completely without carbon dioxide for large parts of the day. Overnight, carbon dioxide is replenished, and aquatic CAM plants take advantage of this condition to fix the plentiful supply of carbon dioxide available at night and store it as malic acid.


Hit my threshold where I just say.. "It's complcated"...


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## Edward (Apr 11, 2005)

That is fascinatingly complicated, thank you @ jeffkrol


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## Deanna (Feb 15, 2017)

jeffkrol said:


> so it's possible "dark" CO2 injection can increase photosynthesis.
> Question is .. How much would it effect it?


That is the great mystery and what provides enough grist to support both "dose it at night" and "don't dose it at night" arguments. Probably best to try it both ways in a tank and do your best to observe the results in order to make a decision.



jeffkrol said:


> IF you run known CAM aquatic plants why inject CO2 in daylight..


That would be an excellent test. However, if you have a mix of CAM and non-CAM plants, you will need it, at least, with lights on.

It's been an interesting discussion (especially the CAM revelation). For my part, I'm starting by moving CO2 on-time to natural dawn (in case ambient light starts photosynthesis), even though lights are on at 10AM and adding blue light at 9AM, assuming a gradual awakening is more natural. After watching for a while, I'll add CO2 24/7, as I have dwarf sag (possible CAM plant), and observe.


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## doylecolmdoyle (Sep 22, 2015)

I too run all my tanks 24/7 co2, always had good results and no ill effects to my fish, make sure surface agitation is high.


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## burr740 (Feb 19, 2014)

Ive inadvertently left the co2 running all night 2-3 times.

Every time I was amazed the next day how soon pearling began. Literally 30 minutes after the lights came on the tank was a rolling boil, like it usually looks 5-6 hours into the photo period.

Always wondered what exactly happened to cause that. From reading the above sounds like photosynthesis might have been a lot more intense(?) right from the start?

Seems odd because there's about a 1.2 drop in PH by the time lights come on. CO2 is already high so it has to be something that occurred over the course of the night


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## Nschubert (Apr 26, 2018)

As stated above C02 is only beneficial for plants using c4 photosynthesis other wise it's a waste. Reason some have pearling as soon as the lights turn on is because they properly saturated the water with C02 so that when the lights turn on there is plenty of carbon for any c3 plants (majority of plants) to use. This can be done by having c02 turn on before the lights. Some plants use c3 and c4. Plants use c4 photosynthesis in the desert where it's more efficient to absorb c02 at night when there's more available H20.
The question is are there any aquatic plants using c4...

Sent from my SM-G892A using Tapatalk


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## burr740 (Feb 19, 2014)

Nschubert said:


> Reason some have pearling as soon as the lights turn on is because they properly saturated the water with C02 so that when the lights turn on there is plenty of carbon for any c3 plants (majority of plants) to use. This can be done by having c02 turn on before the lights.


Did you read my last sentence?  CO2 kicks on 2 hours before the lights, there's a 1.2 drop in PH by the time the lights come on. So that doesnt explain my particular experience.


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## Nschubert (Apr 26, 2018)

burr740 said:


> Did you read my last sentence?  CO2 kicks on 2 hours before the lights, there's a 1.2 drop in PH by the time the lights come on. So that doesnt explain my particular experience.


Essentially to avoid c02 causing a pH change you need to find the right amount of time to saturated the water with out swinging the pH. It's different for every aquarium I recommend and hour to 30 min before lights turn on.

Sent from my SM-G892A using Tapatalk


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## Deanna (Feb 15, 2017)

@burr740:

In starting this investigation, my thinking/wondering was/is around when photosynthesis actually begins, i.e.; how much light (PAR) is necessary to start it up. Based upon what I found (see above posts), it takes very little light, although I could find no PAR (or other) measurements to indicate the intensity needed to start photosynthesis. This lead me to think that ambient light from the sun, at dawn and in the room where your tank is, is enough to start photosynthesis and that CO2 may be better started before dawning of the sun, in such an environment. This could explain your pearling - perhaps the plants had already started photosynthesis long before your CO2 came on. So, by the time your lights hit, your plants were ready to pop.

Rhetorical question: If that is true, and we don't start CO2 earlier, is there enough ambient light to make the plants 'gasp' for CO2, thus creating an opening for algae?

Bump:


Nschubert said:


> As stated above C02 is only beneficial for plants using c4 photosynthesis other wise it's a waste. Reason some have pearling as soon as the lights turn on is because they properly saturated the water with C02 so that when the lights turn on there is plenty of carbon for any c3 plants (majority of plants) to use. This can be done by having c02 turn on before the lights. Some plants use c3 and c4. Plants use c4 photosynthesis in the desert where it's more efficient to absorb c02 at night when there's more available H20.
> The question is are there any aquatic plants using c4...
> 
> Sent from my SM-G892A using Tapatalk


There is a difference between C4 plants and CAM plants. It has to do with the pathway used and the ability to move between night and day. Here is an article that describes the subtle difference:
https://www.khanacademy.org/science/biology/photosynthesis-in-plants/photorespiration--c3-c4-cam-plants/a/c3-c4-and-cam-plants-agriculture

As far as which aquatic plants might be CAM plants, they are in one of my posts, above.


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## Xiaozhuang (Feb 15, 2012)

BTW, Karen uses timer on all of her tanks nowadays. She used CO2 24/7 in the cases of DIY CO2 when rates couldn't be controlled. Barr, her, Amano, myself etc all use timers.... Unless you grow better plants than us, I really do not think there is a need to reinvent the wheel. The pH flux does nothing in 99% of cases.

This is her comment on pH fluctuations - she measures them in natural habitats often in her trips.


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## Nschubert (Apr 26, 2018)

Deanna said:


> @burr740:
> 
> In starting this investigation, my thinking/wondering was/is around when photosynthesis actually begins, i.e.; how much light (PAR) is necessary to start it up. Based upon what I found (see above posts), it takes very little light, although I could find no PAR (or other) measurements to indicate the intensity needed to start photosynthesis. This lead me to think that ambient light from the sun, at dawn and in the room where your tank is, is enough to start photosynthesis and that CO2 may be better started before dawning of the sun, in such an environment. This could explain your pearling - perhaps the plants had already started photosynthesis long before your CO2 came on. So, by the time your lights hit, your plants were ready to pop.
> 
> ...


Yep I just said c4 as c4 and cam use the same pathway just at different times. Some consider CAM an evolution stemming from c4 photosynthetic plants.

Thanks I guess I didn't see the list!

Sent from my SM-G892A using Tapatalk


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## Deanna (Feb 15, 2017)

Xiaozhuang said:


> BTW, Karen uses timer on all of her tanks nowadays. She used CO2 24/7 in the cases of DIY CO2 when rates couldn't be controlled. Barr, her, Amano, myself etc all use timers.... Unless you grow better plants than us, I really do not think there is a need to reinvent the wheel. The pH flux does nothing in 99% of cases.
> 
> This is her comment on pH fluctuations - she measures them in natural habitats often in her trips.


Next: try to convince people to ignore pH when acclimating new fish and focus upon TDS! Talk about a myth!


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## Edward (Apr 11, 2005)

Deanna said:


> In starting this investigation, my thinking/wondering was/is around when photosynthesis actually begins, i.e.; how much light (PAR) is necessary to start it up. Based upon what I found (see above posts), it takes very little light, although I could find no PAR (or other) measurements to indicate the intensity needed to start photosynthesis. This lead me to think that ambient light from the sun, at dawn and in the room where your tank is, is enough to start photosynthesis and that CO2 may be better started before dawning of the sun, in such an environment.


Since the beginning of this hobby, I don’t want to say how long ago, was this “law”, never let sunlight shine your aquarium or algae will flourish. It was thought, at that time, that sun is too strong for aquatic plants. 

Today, we know little more. The reason was not the Sun superior intensity, but it was the disruption of plant’s day night cycle. This was more prominent when the lights were timed to evening or night hours in rooms with *windows*.


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## Deanna (Feb 15, 2017)

Edward said:


> Since the beginning of this hobby, I don’t want to say how long ago, was this “law”, never let sunlight shine your aquarium or algae will flourish. It was thought, at that time, that sun is too strong for aquatic plants.
> 
> Today, we know little more. The reason was not the Sun superior intensity, but it was the disruption of plant’s day night cycle. This was more prominent when the lights were timed to evening or night hours in rooms with *windows*.


Yup, and Dr. William Innes warned us about this in the first few pages, but he did recommend placement in northern light. Interestingly, he said that if you have enough light to read a newspaper by, your plants will have enough light also. Direct sunlight was ok, but no more than 2 hours. Of course, the only alternative was a 40w incandescent bulb.

So, in a room with windows, facing north, with curtains drawn, how much light fills the room at dawn and is it enough to start photosynthesis? As you said; "Today, we know little more."


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## Xiaozhuang (Feb 15, 2012)

Deanna said:


> Next: try to convince people to ignore pH when acclimating new fish and focus upon TDS! Talk about a myth!


lol, couldn't tell whether you were agreeing or disagreeing with her. 
Generally speaking, pH fluctuations within the range that the type of livestock is used to is harmless as long as the pH flux is not indicative of a kH change. You can test this (I do on cull shrimps) - and do the same for other variables. 
Barr's explanations below:
https://barrreport.com/threads/ph-swings-from-c02-danger-to-fish.3801/


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## Deanna (Feb 15, 2017)

Xiaozhuang said:


> lol, couldn't tell whether you were agreeing or disagreeing with her.
> Generally speaking, pH fluctuations within the range that the type of livestock is used to is harmless as long as the pH flux is not indicative of a kH change. You can test this (I do on cull shrimps) - and do the same for other variables.
> Barr's explanations below:
> https://barrreport.com/threads/ph-swings-from-c02-danger-to-fish.3801/


Full agreement with her.


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## Edward (Apr 11, 2005)

Xiaozhuang said:


> BTW, Karen uses timer on all of her tanks nowadays. She used CO2 24/7 in the cases of DIY CO2 when rates couldn't be controlled. Barr, her, Amano, myself etc all use timers.... Unless you grow better plants than us, I really do not think there is a need to reinvent the wheel.


 For me it is not about growing better plants, it is about having fewer components to worry about.

TDS? That’s right, I’ve been promoting TDS since 2004, it’s cheap, fast and easy, and it is more important than pH and KH. I don’t even know what pH and to some extent KH in my aquariums is. What is important is to have consistent TDS and making sure CO2 dissolves.


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## dukydaf (Dec 27, 2004)

dukydaf said:


> There is no need to run CO2 at night, plants will not use it when lights are off.





Edward said:


> Do you know of any evidence about plants not taking or using nutrients at night?


 @Edward , as my post and this thread refer to CO2, I will answer focusing on it. I will not go into details about other nutrients as it would take to long and I did not state anything about them. Suffice to say, many are taken up at night as well, plenty of studies out there , google scholar is your friend. I also limited myself to "use" during lights off... the take has a little star attached to it: 

*Photosynthesis can only happen during the light period.*

I will try to shortly describe how CO2 use works in plants, but this is like describing a car by saying it has an engine, 4 wheels and a steering device. 

Plants need energy to fix CO2 in their tissue, that energy is provided by photons. In simple terms, the photons excite the chlorophyll(p680,p700) which is able to generate ATP and NADPH and release O2(from H2O). The ATP and NADPH provide energy to the Calvin Cycle to create more complex carbohydrates.

*Classic plants C3 *


Light+H2O -> ATP(from ADP)+NADPH(from NADP+)+O2

3CO2+3RuBP(via RuBisCo)->6PGA (uses up 6ATP and 6NADPH)->5G3P-> reused for RuBP (also uses 3ATP)
->1G3P -> make carbohydrate

Rubisco can "fix" CO2 and O2. 
*1glucose produced needs 18ATP+12NADPH*

*C4 plants-high efficiency photosynthesis in high temperature*

CO2+PEP(via PEPc)->Oxaloacetate->Malate or Aspartate-> transport to bundle sheath cells -> CO2(reacts to RuBP as above)+C3acid(PEP)(goes back via 2ATP use )

PEPc can only fix CO2. 
*1glucose produced needs 30ATP+12NADPH*


*CAM plants - limit water loss*
fixes CO2 like C4 plants. At night they take up CO2 and store it as malic acid in the vacuoles. At day the actual CO2 use starts in the Calvin cycle .
*1glucose produced needs 30ATP+12NADPH+ vacuole formation/storage*

So no matter the plant type, no light means no ATP for CO2 use. Obviously, there is still ATP in the cells but if plants were to use it for such an energy expensive process the energy input would be greater than the output => plants will eat itself up and die. So again, no plant uses CO2 in the dark. And with the exception of aquatic CAM-like plants, no aquatic plants take CO2 up during the dark phase. 

Let's talk a little bit more about the CAM-like plants. Someone said that there were many.Yes many as in more than 2 but a very small % in reality. Unlike terrestrial CAM plants which developed the CAM pathway to prevent desiccation during the day, aquatic plants adapted to make use of the high CO2 conc. observed during night times. Not surprisingly then, plants which are adapted to long periods of time underwater have this CAM-like pathway: sagittaria, vallisneria and littorella. So these 3 are relevant to the hobby, all 3 grow like weeds even in the simplest aquariums. *Is it worth keeping CO2 at night for them ?*?? Also, worth mentioning that if there is enough CO2 during daytime they will take it up and use it directly, without the need to store it. The article by Keeley(1998) has plenty of juicy details. 

Most plants we have in aquariums are aiming for one thing, grow out of the water and get in contact with the atmosphere, no need to develop an energy expensive process like CAM for this. You have water at your roots, the sun shining on your leaves and CO2 flooding your stomata.



Edward said:


> Turning CO2 at night off allows pH go up making precious Fe, Mn Zn and Cu bioavailability go down. Also, it lowers chelating ability to protect these essential nutrients from becoming non-bioavailable. They become oxidized, unusable and insoluble part of substrate. No water change can then remove them. Plants and fauna will do better not because of CO2 addition at night but because of the pH effect it has.


In the last sentence you are saying that the pH has an effect on fauna. What is that ? How strong is that in the normal aquarium pH range (8-6pH)? What daily pH changes do not affect fauna and how stable should stable be ?

For the normally targeted 1pH drop from degassed, with normal aquariums it will typically go 0.5 pH up overnight. In many situations this still results in a pH<7, so the chelators should hold. Plus higher pH means other nutrients become more available, Mo for example. With all this high tech it is easy to dose more frequently than once per week and even more than once per day. A good substrate vacuum with the water changes will get rid of any precipitates.


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## Whysoserious (Dec 7, 2017)

dukydaf said:


> For the normally targeted 1pH drop from degassed, with normal aquariums it will typically go 0.5 pH up overnight. In many situations this still results in a pH<7, so the chelators should hold. Plus higher pH means other nutrients become more available, Mo for example. With all this high tech it is easy to dose more frequently than once per week and even more than once per day. A good substrate vacuum with the water changes will get rid of any precipitates.


_In many situations_ on this forum, people are making changes to dosed salt concentrations in the range of tenths of a part per million, for _various_ reasons. Maintaining pH via CO2 (with everything else being equal) is good practice in the stability of ions (when targeting tenths of a part per million).

Besides, you're arguments against, are three assumptions that (suitably) narrows the range of aquariums that fit within the bounds of your statements, a random statement about chelators, the odd-ball case supporting higher pH, and some nonsense about doing more work being easier then doing less work.

I really appreciate the time and detail in your discussion regarding photosynthesis and C3/C4/CAM plants. Although, I don't see anything that says CO2 running during the dark period is problematic, and indeed, your describe some species of hobby plants that do actually have the mechanisms to exploit increased CO2 concentration during dark periods. 



> How strong is that in the normal aquarium pH range (8-6pH)?


Pourbaix diagrams show that most micro-elements move from predominately soluble, to predominately insoluble from 6-8pH.


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## jeffkrol (Jun 5, 2013)

> Maintaining pH via CO2 (with everything else being equal) is good practice in the stability of ions (when targeting tenths of a part per million).


awaiting data.. Like I said using a pH monitor will not stop pH from dropping lower than the set point..

Will not let it go higher but as "accumulated" daytime CO2 and nightly respiration drop the level.. How.. in reality "steady" is it?
to be honest, can't find any 24/7 pH charting CO2 or not.

W/ the amount of Seneyes out there should get easy..


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## Whysoserious (Dec 7, 2017)

jeffkrol said:


> awaiting data..


For what exactly?



jeffkrol said:


> using a pH monitor will not stop pH from dropping lower than the set point..


Correct, reducing alkalinity sufficiently, to lower the pH below the pH which is otherwise obtained via CO2 injection, will cause pH to drop below the set point of a pH controller controlling CO2. 
When I had a pH controller controlling CO2 injection, I was still concerned with KH, but maybe that's just me.

One of the advantages of CO2 is it's lack of reaction with alkalinity. CO2 shifts pH to the left on the Bjerrum plot, _*not *via transformation_ _of the chemical species_ (less of one and more of the other), but by the simple addition of a chemical species. The alkalinity (which is buffering the pH) does not reduce in concentration.

If you create a set of circumstances where the alkalinity is reducing to the point of causing a pH crash, the problem isn't CO2, nor the method with which it's injection is being controlled. The problem is the reduced alkalinity.


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## jeffkrol (Jun 5, 2013)

Whysoserious said:


> For what exactly?


Data not hearsay and innuendo..
Nano reef tank example:


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## ChrisX (May 28, 2017)

*dfg*



Robert42 said:


> Thanks for your reply. I have not considered using a pH Controler. I would like to hear from anyone just running the CO2 overnight as well as the day.


I have used CO2 24/7 this past year. The level of CO2 will depend greatly upon how much agitation there is. Off gassing has a greater effect on the CO2 concentration than the amount you add.

It turns out that using constant CO2, I only needed 1bps. When using the solenoid, I would need 3bps to bring the level back to 30ppm, and it would need to be on 3 hours in advance of lights.

However, when I later added a HOB, the additional churn gassed off a ton of CO2, so it is not practical to use 24/7. I ended up using a venturi on a power head 24/7 to introduce oxygen and this did not have the effect of gassing off CO2 like the HOB did.

Its a balancing act. If you have alot of surface agitation, I would use the solenoid.

BTW, I am back to using [email protected] 8 hours/day to experiment and I'm not noticing any difference from the past year in plant health or growth, although I am able to use the HOB now.


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## houseofcards (Mar 21, 2009)

There is zero reason to run co2 24/7 for plant health purposes, but it is more likely to affect fish health for those less experienced.


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## Whysoserious (Dec 7, 2017)

jeffkrol said:


> Data not hearsay and innuendo..


If you could piece together a coherent argument explaining how the quote is not factual, rather then taking pot shots from your trojan horse, that would better reflect your contributions to this community.

edit: I think you're trying to argue that injecting CO2 via a pH controller does not keep pH extremely consistent, which of course is correct. But what is the relevance (to the argument at hand)? There's a reason I used parenthesis "(with everything else being equal)".

If you tone down on the "I said" statements, and follow the quoted argument, it began with, 



Edward said:


> The goal is to offer plants enough nutrients day and night so they can store it and be ready for the next light period. Turning CO2 at night off allows pH go up making precious Fe, Mn Zn and Cu bioavailability go down. Also, it lowers chelating ability to protect these essential nutrients from becoming non-bioavailable. They become oxidized, unusable and insoluble part of substrate. No water change can then remove them. Plants and fauna will do better not because of CO2 addition at night but because of the pH effect it has.


Irrespective of how accurate pH remains with the use of a pH controller and CO2, pH will always be lower with consistent injection of CO2 (vs no injection of CO2), resulting in the quoted paragraph above being an accurate and factual statement.


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## jeffkrol (Jun 5, 2013)

Whysoserious said:


> If you could piece together a coherent argument explaining how the quote is not factual, rather then taking pot shots from your trojan horse, that would better reflect your contributions to this community.
> 
> edit: I think you're trying to argue that injecting CO2 via a pH controller does not keep pH extremely consistent, which of course is correct. But what is the relevance (to the argument at hand)? There's a reason I used parenthesis "(with everything else being equal)".
> 
> ...


you take me way too serious..

What I meant is there is no

pH levels over 24 hours time (natural tank):
{CHART}

CO2 injected (daytime only) pH change over 24 hours time:
{CHART}

CO2 injected 24/7 pH over 24 hours time (could break it down to controller controlled or bubble counter):
{CHART}



Compare/contrast discuss..



> This is the second time that I have tested at night and my PH is 7.9 and when i test again in the morn it will be about 7.5


Read more: PH changes night and day - Tropical Fish Keeping - Aquarium fish care and resources

Not really good enough type of data for any meaningful discussion really..



> Turning CO2 at night off allows pH go up making precious Fe, Mn Zn and Cu bioavailability go down


quantify it..Is a "going up" pH of 7.2 to 7.3 relevant.

Like I said needs data...

Ahhh.. I see, led you to believe it was data from you.. no , that was unintentional sorry..


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## Whysoserious (Dec 7, 2017)

jeffkrol said:


> you take me way too serious..


Thanks for the chuckle.



jeffkrol said:


> quantify it..


I already did.



Whysoserious said:


> _In many situations_ on this forum, people are making changes to dosed salt concentrations in the range of tenths of a part per million, for _various_ reasons.............Pourbaix diagrams show that most micro-elements move from predominately soluble, to predominately insoluble from 6-8pH.


I do not have the data _or the knowledge_ to accurately describe what a random change in pH has on the (specific) availability of ions, or the (specific) downstream effects on a plants ability to grow under those changing conditions (from pH 6.5 to pH 7.0 has these specific effects on plant growth, affecting growth by this specific percentage, for example). What I do know, and that pourbaix diagrams describe, is that rising pH (6.0 > 8.0) has a negative effect on the solubility (availability) of ions. And thus, even without data to quantify the specifics, Edwards quoted statement is factual and correct***.

To quantify it further in regards to the typical discussion on this forum. Joe bloggs changes a micronutrient concentration from 0.08ppm to 0.05ppm and the next day he says he sees positive reaction in the appearance of his plants. But when he's told that higher pH has some effect on the availability of ions (equal to a concentration change), _likely_ above the effect from the typical micro changes in micronutrient concentrations that generate long heated discussions on this forum, every man and his dog tries to dispute the factual evidence presented as meaningless.











*** A good accurate general guideline.


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## jeffkrol (Jun 5, 2013)

You are missing the point slightly..

Lets put it this way....
with a pH controller set to 6.8 on a normally buffered tank (eh) and running 24/7 what is the pH at 3 AM?
Same for one w/ the above parameters but off at say 6 pm..


Obviously it is 6.8.. (kicker) or less.. nobody seems to know..
Won't go up hopefully.


Without that talking about ionization rates (or equilibriums of reductive states) at a given pH is sort of...pointless.. 

There seem to be lot of assumptions i.e running 24/7 CO2 keeps the pH constant, that aren't "exactly" proved..
It's likely correct but likely isn't a fact..

We do have an idea of what nature does.








http://www.krisweb.com/krissheepscot/krisdb/html/krisweb/analysis/hypoth_5_wq_sheep.htm

Again. I just want to know "exactly" how pH fluctuates under the different "systems" first. worry about mineral uptake/availability/equilibrium later..
LOT of this w/ zero actual data..



> Why do people try to get rid of the "extra" CO2 at night? If anything you get less pH swing and more starting CO2 in the morning if that "extra" CO2 stays in the tank. Am I missing something?
> .


Data.. 

https://barrreport.com/threads/co2-on-off-and-ph-fluctuations.5149/


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## houseofcards (Mar 21, 2009)

Does anyone know how old that article is that the OP linked? As pointed out by @dukydaf there is a lot of old and/or debunked information contained in it IMO.


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## Whysoserious (Dec 7, 2017)

pH controllers are designed, manufactured, marketed and sold in significant numbers to _perform a specific task_. With CO2 use to reach a low pH end point (pH controller set to use CO2 to reduce pH until it reaches the pH setpoint set by the user), there can be only two failures to reach this set pH end point. Not enough CO2, faulty controller. 

If you're targeting a 1.0 pH or greater pH drop using CO2, and the pH starts dropping below the setpoint of a pH controller, the issue isn't CO2, or the controller, it's a water quality issue. A separate water quality issue that has nothing to do with with this discussion. KH (alkalinity) is important in and of itself (regardless of CO2 and pH controllers).

If you have CO2 on 24/7 without a pH controller, then pH will fluctuate, because CO2 is no longer being used to control pH, simply that the concentration of CO2 is being increased by some margin above equilibrium with the atmosphere. With a pH controller, you are purchasing a specific instrument to perform a specific task.

The variations of pH in nature describe the happenings of a system that doesn't have CO2 control via pH. Nature doesn't have a CO2 cylinder hooked up to it with the rate of injection controlled. Nature has a specific CO2 concentration available to it bound by Henry's law (there are specific cases such as a bog where other processes have a greater effect on CO2 concentration then the atmosphere). If nature did have pH controlled CO2, the graph you posted would be significantly more bound around the pH setpoint, because as the CO2 is consumed by the plants (the concentration of CO2 in the water is reduced, the concentration of H2CO3 is reduced, and the equilibrium of the bjerrum plot for carbonate species is shifted to the right), and pH begins to rise, the pH controller would just keep injecting more and more CO2 to compensate to reach the desired pH (because the pH controller is a specific instrument designed to perform a specific task).

All other things being equal (KH concentration remains relatively fixed for example), the only fluctuations in pH with a pH controller are due to controller accuracy (there's usually some margin between the desired pH setpoint, and when the controller will actually decides correct for pH changes), and the lag in the ability to dissolve CO2 into the water. 

You keep screaming for data, the data is in pourbaix diagrams. Someone being able to post fancy graphs detailing their ability to maintain steady pH (or otherwise) doesn't change pourbaix diagrams or the validity of the original quoted statement.


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## jeffkrol (Jun 5, 2013)

"sigh"....................................

BTW nature does have CO2 "bottles" hooked to it.. It's called for one Bacterial (and others) respiration...............




> (there's usually some margin between the desired pH setpoint, and when the controller will actually decides correct for pH changes), and the lag in the ability to dissolve CO2 into the water.


You know how one could quantify that.. W a {CHART}..


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## Whysoserious (Dec 7, 2017)

jeffkrol said:


> BTW nature does have CO2 "bottles" hooked to it.. It's called for one Bacterial (and others) respiration...............


And yet, pH rises in natural waters as shown by the graph you posted. So those bacteria could probably be called PMDD bacteria, not EI bacteria.

I would absolutely [censored][censored][censored][censored]ing adore to have the time, inclination and skillset to better educate in an efficient manner. Truth of the matter is that time is limited (because family is more important) and at some stage in life, people have to take on the responsibility of education upon themselves.


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## Nschubert (Apr 26, 2018)

In nature pH if affected by alooooot of other inputs and isn't as highly correlated to c02 levels. When arguing sitiations in nature vs in an aquarium the connection cannot be simply made. In a closed system such as an aquarium you have to mimic all the inputs from bacteria (c02) and from ripiran zones and veg in the water and upstream intups and.......

One can not say then that bc it went down in the pond behind my back yard or in some river that you can come close to recreating that exact environment and it's affect on tank parameters.


Sent from my SM-G892A using Tapatalk


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## jeffkrol (Jun 5, 2013)

Whysoserious said:


> And yet, pH rises in natural waters as shown by the graph you posted. So those bacteria could probably be called PMDD bacteria, not EI bacteria.
> 
> I would absolutely [censored][censored][censored][censored]ing adore to have the time, inclination and skillset to better educate in an efficient manner. Truth of the matter is that time is limited (because family is more important) and at some stage in life, people have to take on the responsibility of education upon themselves.


Why so serious... 

Bump:


Nschubert said:


> In nature pH if affected by alooooot of other inputs and isn't as highly correlated to c02 levels. When arguing sitiations in nature vs in an aquarium the connection cannot be simply made. In a closed system such as an aquarium you have to mimic all the inputs from bacteria (c02) and from ripiran zones and veg in the water and upstream intups and.......
> 
> One can not say then that bc it went down in the pond behind my back yard or in some river that you can come close to recreating that exact environment and it's affect on tank parameters.
> 
> ...


right, which is why concrete data on tanks is err.. required...
how does one know what the pH is doing if it's not measured or measured "sporadically"

I certainly don't see where I'm going is "unreasonable" in the least..

sad thing is I could do it myself, though no pH controller and don't want to mess w/ my current delivery..
surprised that it hasn't been done.. or at least common..
lot of pH does this that and the other thing.. few numbers..

Granted tanks are like nature in the fact that all are "different" to a degree...

hey,,, CHARTS.. 
https://www.ukaps.org/forum/threads/co2-ph-level-in-planted-tank.26559/










SADLY.. not pH..


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## Robert42 (Aug 16, 2017)

Thank you, everyone, for a very interesting discussion that did go over my head at times. For some reason, the posting update had stopped coming in so I only get the weekly update last night. It is good to see people being so passionate about the hobby. I have been running CO2 continuous for about a week but no livestock in the tank. I am hoping yo keep constant CO2 levels to keep the algae at bay. In my low tech shrimp tank that is full of moss and a couple of stem plants, I do little. I like some algae to grow but I notice that if I use ferts the plants grow and the algae don't.


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## jeffkrol (Jun 5, 2013)

Robert42 said:


> I am hoping yo keep constant CO2 levels to keep the algae at bay.


consistent is best.. 

BTW: In my never ending pursuit of being a true PIA, found this..


> Here is my question on setting up my controller...with Discus (or any sensitive fish), should I:
> 
> 1) run my CO2 24 hours a day with the controller auto shutting it on and targeting a specific PH - I have tested it and can keep it very stable at 6.3 to 6.5, and still get ample CO2 into the tank. This way the PH of the tank will be at this value 24x7 as I will be running the CO2 at night as needed for this PH.
> 
> 2) run it on the 10 hour lighting cycle, shutting it off at night and allowing the PH to creep back up to 6.8 or 7. This way the daily PH flucuation with by 6.3 or 6.5 to 6.8 or 7, not insignificant, but not huge.


http://www.plantedtank.net/forums/8.../1207146-question-re-ph-controller-w-co2.html


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## burr740 (Feb 19, 2014)

jeffkrol said:


> Has less to do w/ it than one thinks...


What makes you say that?

Inconsistent CO2 levels from one day to the next will bring on algae as fast as anything, specifically bba.


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## jeffkrol (Jun 5, 2013)

burr740 said:


> What makes you say that?
> 
> Inconsistent CO2 levels from one day to the next will bring on algae as fast as anything, specifically bba.


corrected it.. but thanks .. 
Sadly, was just thinking CO2 in general..

I'd discuss the above re: BBA w/ my own trials and tribulations but ..... naaahh.
Lets' just say even consistent CO2 w/ out other factors means little. in my experience.
no more than bright lights cause algae..



> 2) run it on the 10 hour lighting cycle, shutting it off at night and allowing the PH to creep back up to 6.8 or 7. This way the daily PH flucuation with by 6.3 or 6.5 to 6.8 or 7, not insignificant, but not huge.


remember this:
Most tanks (certainly those w/ solenoids) will have fluctuating CO2 levels to a certain extent..


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## houseofcards (Mar 21, 2009)

Every hi-tech tank has fluctuating co2 levels. It's called a water change. BBA would only be brought about if the uptake of the plants was insufficient to deal with the organic load.


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## burr740 (Feb 19, 2014)

jeffkrol said:


> corrected it.. but thanks ..
> Sadly, was just thinking CO2 in general..
> 
> I'd discuss the above re: BBA w/ my own trials and tribulations but ..... naaahh.
> ...


Well you can say it however you want to but having stable co2 levels from one day to the next is very important. 

Unless you're bouncing around always above a non-limiting level. But going from plenty to not enough and back again is asking for trouble.


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## houseofcards (Mar 21, 2009)

burr740 said:


> ...But going from plenty to not enough and back again is asking for trouble.


Agree


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## Greggz (May 19, 2008)

burr740 said:


> Unless you're bouncing around always above a non-limiting level. But going from plenty to not enough and back again is asking for trouble.


I think what you said there is the key. Bouncing around always above a non-limiting level is different than from plenty to not enough.

I run a pH controller, and my pH drop drifts in a range from 1.3 to 1.4 for the lighting period. Now if something happens, and let's say my drop is only 1.1, I see signs. I can tell right away something isn't quite right. And it's the first thing I'll check, and take the time to be certain I have it right.

In my experience, once plants get used to a certain level, they rebel pretty quickly if you take it away. Goes to my general thoughts on stability in general. I know in my tank, my plants don't seem to like sudden changes, whether that be CO2, lighting, or ferts (or lack of maintenance as well). 

I also think that effect gets turbo charged when you have very high lighting and fast growing flowery stems. Less room for error and much quicker changes. My guess is that you would have less intense reactions in a lower light environment.

Now I've got no horse in this race, but as soon as my lights go off, so does my CO2. Then the heavy air stone aeration begins and goes all night until the next CO2 period. If nothing else, I'm sure my Bows appreciate the highly oxygenated water overnight.


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## houseofcards (Mar 21, 2009)

Generally I agree with that's being said, but definitely will depend on tank. If you take a tank that has very hi light, low plant mass and you need to change the water every day or every other day to keep it pristine, technically it has more co2 flux, but the organic load is less. The effect of removing water to me anyway is greater then some changes in co2 levels and it's effect on algae growing. BBA to me will always be about organic load and insufficient plant mass and BB.


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## burr740 (Feb 19, 2014)

Water changing a high tech tank shouldnt cause a big swing in co2 unless you do it in the middle of the light cycle. Even then it's going right back up in an hour or two from injection. Ideally its best to do water changes right before the lights come on

Most tap is pretty rich right out of the faucet anyway, but not rich enough to cause a spike in a co2 injected tank. (Low techs are a different story)

Unhappy plants spark most algae including bba. A prime example is plants stalled out because they cant figure out how much rubisco to make because co2 is up and down. It is an expensive enzyme to make as far as resources go, and it doesnt happen overnight. Plants take time to adjust

That's one reason why Barr and Wong and most other gurus are adamant that bba is a co2 problem

Although I do agree about organic waste also being a direct cause. Definitely


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## houseofcards (Mar 21, 2009)

If I'm being honest I never do water changes with lights off. I've always done them whenever, usually right in the middle of the day and never had an issue. If your removing the typical 50% then that's a pretty big drop in co2 with lights on. Just saying to me the co2 is about uptake and the removal of waste at a certain level that the tank is good with. Not that much different then a water change, carbon, etc. 



burr740 said:


> ...That's one reason why Barr and Wong and most other gurus are adamant that bba is a co2 problem


I used to argue this point with Barr alot and he never gave me a satisfactory explanation. The co2 and bba connection yes, it does make sense but not in a vacuum only in respect to plant mass. In a thinly planted tank all the co2 in the world or all the consistent co2 will not keep algae away if their isn't even plant mass to deal with the organics in the tank.


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## Whysoserious (Dec 7, 2017)

jeffkrol said:


> Lets' just say even consistent CO2 w/ out other factors means little. in my experience.


CO2 is as you say, simply a piece of the puzzle.
The problem with ocean acidification, isn't rising CO2 levels _per se_, but the speed with which the change is occurring.

http://www2.luresext.edu/aquaculture/Limnology lectures/Chap 13carbondioxide.pdf
http://files.dep.state.pa.us/Public...ination Protocol 20171025 WRAC for Policy.pdf
http://files.dep.state.pa.us/Public...ation Protocol AG Advisory Board 20171221.pdf


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