# Can you have too much CO2????



## toadass

Hi all

I was just reading one of Viktor Lantos journals and he mentioned in there something about how too much CO2 can cause algae. I can't remember off the top of my head what it was...... Staghorn i think, i'm not saying i disagree with Viktor because i have seen the great work he scapes, and the health of his plants always looks superb. It's just i was under the impression that you can inject as much CO2 into the tank as the fish can take before they start gasping. If anybody can clarify or has any knowledge of this it would be nice as i'm just intrigued if this is a case   

Thanks Matt


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## George Farmer

If you have so much CO2 (and light) that it causes the plants' nutrient demand to exceed the nutrients available then algae growth may occur.


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## ceg4048

You can never have too much CO2. As George mentions however, CO2 drives an uptake demand for more nutrients. Therefore it is more correct to think of it in terms of algae due to not enough nutrients, instead of in terms of too much CO2. I use too much CO2 all the time and I don't get algae, so algae can't be due to too much CO2. One has to broaden the way one thinks about light, CO2 and nutrients because they are closely related. Thinking about one of these factors without relating it to the others always leads to irrational conclusions.

This happens all the time, for example, when someone changes their tank from a non-CO2 tank to a CO2 tank, or when they go from a lean dosing program to a eutrophic dosing program. They often get algae and then draw the conclusion that CO2 causes algae, or that nutrients cause algae. But changing the environment from an non-enriched to an enriched condition fundamentally affects the way that the plant interacts with that environment, in the same way that going from emmersed to submersed affects the plant interaction. So one has to consider all the factors in the environment as well. The supply of the environment and demands of the plant form an intricate "economy" of energy. This is the best analogy to keep in mind when assessing plant health.

Here are three conditions listed in descending order of severity:
If you add more light then you need to add more CO2 and more nutrients. 
If you add more CO2 then you need to add more nutrients. 
If you add more nutrients then you need to add more CO2.

If you don't consider the dependent variables then the consequence is reduced health, and this triggers algal blooms. It's really very simple at a general "macroeconomic" level but we complicate things by ignoring these dependencies.

Cheers,


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## AngelTM

Unfortunately this is a very old thread, but I still hope that ceg4048 will be able to read this and hope to have a clarification on my thoughts. George Farmer's (a very good guru on planted tanks, I learned a lot from his videos) statement is easy to understand high co2 + hight light without the right amount of nutrients will cause algae.

I find ceg4048 statements very interesting and at the same time very important.
Here are three conditions listed in descending order of severity:
If you add more light then you need to add more CO2 and more nutrients. 
If you add more CO2 then you need to add more nutrients. 
If you add more nutrients then you need to add more CO2.

At present I run my CO2 at 1 bubble per second certainly this is not enough to reach 30ppm. My light is low to medium (based on the lumens rating of my LED lights) running at 7 hours a day but not all three lights all the time, I dose following the concentration of PPS-Pro. Things a are looking good at this settings. I noticed when I tried running my co2 at 2.5 to 3 bubbles per second, having the same light, photoperiod and same dosing that the tank is not as clear or I feel like something is wrong compared when I run my co2 at 1 bubble per second.

Based on ceg4048 statement: "If you add more CO2 then you need to add more nutrients." Does this means it not advisable to increase my co2 (without adjusting lights) to the limit of 30ppm so not to worry about it, without appropriately adjusting my nutrient dosing? or "If you add more nutrients then you need to add more CO2" does this also means that it is not advisable to dose EI based concentration (without adjusting lights) without appropriately adjusting my co2?


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## Tim Harrison

It's a balancing act between interdependent factors. 

If, as in your case, your plants are doing well to start with, adding more fertz and/or CO2 shouldn't adversely affect their health either way, just maybe increase their growth rate. That is if your lighting remains unchanged.
If you add more CO2 without increasing fertz it'll just mean that CO2 will potentially become non-limiting to growth and your fertz will then become the potential limiting factor instead, and vice-versa.

I think the real challenge comes when you start to increase light intensity and photoperiod duration, especially since folk typically use too much of both. Without adequate CO2 and fertz you will run in to trouble, which usually manifests as plant melt and algae.

That's why eutrophic dosing systems like EI work so well, it effectively means that fertz are no longer limiting leaving us to concentrate on getting the flow and distribution of CO2 right, which is the difficult bit.


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## foxfish

I don't think you can add to much C02 if you are using EI ferts, I think the upper limit is around 40ppm of C02, that is what water can hold?
The suggested limit of 30ppm of C02 is more about gassing your fish & to be honest in anything bigger than 120lt 30ppm is difficult enough to hit!
I seem to remember Tom Barr talking about using 40ppm of C02 in one of his tanks?
I have always favoured high C02, low light with EI ferts & generally this formula works vey well for me.


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## Edvet

AngelTM said:


> If you add more nutrients then you need to add more CO2.


i don't agree with this one. I feed my plants quite hard, and don't add CO2. You just have to do your waterchanges.
I probably feed more then needed, but there are no problems ( other then my floaters filling the surface in a week), no algea, black,  blue, green or otherwise.


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## ceg4048

AngelTM said:


> Based on ceg4048 statement: "If you add more CO2 then you need to add more nutrients." Does this means it not advisable to increase my co2 (without adjusting lights) to the limit of 30ppm so not to worry about it, without appropriately adjusting my nutrient dosing? or "If you add more nutrients then you need to add more CO2" does this also means that it is not advisable to dose EI based concentration (without adjusting lights) without appropriately adjusting my co2?


Hi,
    As mentioned by the other posters, these are the general principles regarding the relationship between light/CO2/nutrients and they cover the range of combinations from low to high. So for example a low tech non-carbon enriched tank can get away with minute amounts of nutrient dosing because the CO2 level is low. If carbon was then added to the tank without adjusting the nutrient level upwards then nutrient defficiency would typically occur.

It has often occurred where the hobbyist uses a very low level of nutrients and CO2 where that particular combination results in the tank being CO2 limited. This may work fine until the CO2 is increased. The increased CO2 may then result in a higher demand for nutrition. If no more nutrition is added the tank may then become nutrient limited.

Whether we see problems in the tank as a result of changing one or more of these factors is a matter of severity of change. So for example, changing the injection rate from 1 bps to 2 bps may not make a difference, but changing from 1bps to 6bps may expose the new nutrient limitation.

Trying to determine quantitative values of change is difficult, so T.Barr decided it would be a better strategy to operate at the high end and simply remove the limits. So if CO2, nutrients were unlimited then the tank could withstand strong lighting. This is the basic principle of EI dosing which simplifies this aspect of the light/CO2/nutrient relationship.

In your chosen dosing scheme, Perpetual Preservation System, it is entirely possible that increasing the gas injection rate beyond the current limits may expose a nutrient limitation. Of course, we do not really know whether your tank is light limited, CO2 limited, or nutrient limited. This is the pitfall of applying general statements to a specific case. PPS is a very uncertain scheme because it depends a lot on measurement results of the nutrient levels, which is fundamentally uncertain. It could be, for example, that you water source is already high in nutrients so that even a large change in the gas injection rate does not cause any problems, or, the opposite might be true and a large injection change exposes nutrient related issues. I cannot predict, however, it's more important to be aware of the possibilities so that you understand what's going on and can take the proper corrective action if necessary.

To this end, it is also necessary to be able to determine what symptoms indicate a CO2 shortfall as opposed to symptoms that indicate a nutrient shortfall.

One thing for certain, as foxfish mentions, is that you never need to adjust the light intensity upwards. Excessive lighting causes more problems than it solves and reduces your margin of erorr , so if your lighting is low to moderate then you have much more room to make adjustments to either nutrients or to CO2 without incurring problems.

Cheers,


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## AngelTM

Thanks. I can understand that the best way to go is to have non-limiting nutrients and non-limiting co2 and just set the lights according to my needs. Assuming that my lights and nutrients are balance at the moment. Does increasing my co2 to 30ppm potentially leads to problem like having algae or plant deficiency? As what toadass is trying to clarify.


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## ceg4048

Hi Angel,
               Well really, as foxfish mentions, 30ppm is an arbitrary number set as a safety limit for the fauna. Depending on temperature, pressure  and surface agitation, it is possible to saturate the water to very high levels of CO2. Furthermore, no one actually knows how many ppm is in their water. Additionally the CO2 concentration is not homogeneous across the tank. some areas have more than others. We attempt to rectify this by paying attention to flow rate and distribution techniques. Only about 10% of the gas you inject actually makes it to the plants. The rest goes straight out the top of the tank. It's therefore very difficult to achieve non-limiting CO2 without annihilating your fish. The best policy we have discovered is, if your alkalinity is medium (say 4dKH -8dKH) then aim for a 1 pH unit drop from the time you turn the gas on to the time the lights go on and to ideally maintain that difference throughout the photoperiod. Of course, these are all just general guidelines.

As we have already discussed above, adding more CO2 in itself cannot cause algae, however it can expose limiting conditions which do lead to algae because of the limits that are exposed.
Now, the OP is confusing the addition of CO2 with poor implementation of CO2. It is an observation that by a wide margin, the most frequent cause of problems in a CO2 injected tank is poor CO2 implementation.
The mechanism strategy by which plants uptake and assimilate CO2 is so complicated that we get it wrong more times than not.

Algae is caused by poor plant health and it is entirely possible and is often the case that the mistakes we make when attempting to feed CO2 we inadvertently damage the plants. Unfortunately, the journal blaming CO2 for causing algae was in error. Ironically, Staghorn Algae is caused by poor CO2 - but I doubt that this is what Viktor experienced. It was likely the case we described where the CO2 was increased without an increase in nutrition, or it could alsio have been the case where Viktor increased both the CO2 and the light but added too much light. It's very difficult to say without having the facts of the case. People blame unrelated factoras as the casue for problems in the tank all the time. Because we understand cause and effect, we can have a go at unraveling the culprit if the facts are provided.

The lighting determines the nutrient and CO2 requirements. Also, we have to consider water flow/distribution which are the elements that become more important as the lighting is increased.

My advice therefore is to first set your lighting to a low intensity while you increase the CO2 and dose unlimited. You will have a much greater chance of success doing it that way. You can then slowly raise the light intensity if you wish.

Cheers,


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## AngelTM

Thanks a lot Clive, these pretty much clears everything.  I really do not have any plans to increase my lights settings. I like the speed my plants grows at this setting. As for flow and circulation another important part of the hobby, a lot has improve when I added additional filter does increasing my surface movement and circulation in turn increasing gaseous exchange. I never intended to have a fast growing tank, this might not be the case for others, its just me. Directly, unbalance nutrients and CO2 will lead to plant health problem in turn indirectly causing algae. Sometimes it gets confusing, it is good there are people here to clear things. If you are not sure as Clive said have a non-limiting nutrient and non-limiting CO2 then play around with the lighting, as attested by foxfish even on low light this works.


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