# Air stone CO2 question



## BulletToothBoris (Jan 17, 2013)

In a non CO2 injection tank will running an airstone non stop reduce available base line CO2?


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## Django (Jun 13, 2012)

I think so. At night, respiration of plants and bacteria increase the amount of dissolved CO2. The CO2 level is higher than the equilibrium level with the atmosphere and the CO2 wants to get out of solution, through the water surface.

When an airstone is used, the surface agitation it creates increases the surface area and lets out CO2 at a higher rate. This would have an adverse effect on the growth of the plants during photosynthetic activity, say in the next light period.

I think the ultimate answer to this question will be found in Chemistry, the Partial Pressure of Gases in Solution. I haven't been able to get a handle on it yet.


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## kman (Dec 11, 2013)

^^ I dont think so. 

Co2 in a given body of water is going to be at equilibrium with the atmosphere. I don't mean they'll have the same exact percentages, because water has different absorption rates for different gasses, but under normal circumstances, an equilibrium IS established. As plants consume co2, the water will actually be out of equilibrium and seek to absorb more more co2 to return to equilibrium. The increased surface exposure from the airstone should help with that, but it's still a relatively slow process. Similarly, the hyper-dissolved co2 will be released at a much faster rate due to the same agitation. 

I could be wrong, but it makes sense based on my understanding.


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## BulletToothBoris (Jan 17, 2013)

Two very good points that both make sense but both can't be right. I'm running an airstone 24/7 right now with no CO2 injection but dosing liquid carbon twice per week. What would some of you more experienced guys do in my situation?


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## roadmaster (Nov 5, 2009)

I run large hydro sponge filter's at night, to help provide more oxygen exchange at the surface for pleco's,loaches,cory's.
Some say plant's produce enough oxygen during the day that what I'm doing is not necessary, but after adding the sponge filter's I stopped seeing these fishes at the surface during the middle of the night. (I get up at midnight).
In any event,,I have seen no detriment to the plant's in my low tech affair's.


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## BulletToothBoris (Jan 17, 2013)

So maybe I sould just run it at night.


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## roadmaster (Nov 5, 2009)

BulletToothBoris said:


> So maybe I sould just run it at night.


I was more concerned with O2 level's rather than CO2 so I put them on timer to come on one hour after light's off for the day,and go off thirty minutes before light's go on.
I don't think judging from plant's, that I gained or lost anything with regard's to CO2 for it seem's to be what it is in my tank's with no CO2 injection or supplement's. Has not hurt growth which seem's about the same as before I used them.(I think).


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## kman (Dec 11, 2013)

BulletToothBoris said:


> Two very good points that both make sense but both can't be right. I'm running an airstone 24/7 right now with no CO2 injection but dosing liquid carbon twice per week. What would some of you more experienced guys do in my situation?


I have extensive experience with dissolved gasses under pressure as a technical scuba diver. I do NOT have extensive experience with co2 in planted tanks, but I've read a LOT over the past few months, preparing a system of my own.

From what I've read, plants give off enough o2 during the day, while they are in their photo period, that you should not need your airstone during the day, if you're injecting co2. At night, once plants stop photosynthesizing, they also stop absorbing the co2 in the water, so if you continue injecting co2 even at night, you create an imbalance in the water, dangerously towards co2. That's why most people (who need to at all) run an airstone at night. Too much co2 actually interferes with the gills' ability to extract the oxygen that's in the water.

For you, however, you're NOT injecting co2. You're using Excel, or Glutaraldehyde, which provides a similar function to co2 for the plants, in that it provides a source of carbon, but is NOT the same as dissolving actual co2 gas into the water. From a co2 / dissolved gas standpoint, you're not doing anything with your tank. So in that sense, unless your tank is overstocked or capped and doesn't have any opportunity for normal gas exchange at the surface, you shouldn't really need to run and airstone at all. Normal surface agitation from your filter's output should be adequate, just like a 100% vanilla low tech tank.

FWIW, however, and back to the original question, if you're only use liquid co2 like Excel and not actually dissolving co2 gas via injection, running and airstone for 15 minutes or 24/7 will have zero difference to the amount of carbon made available to your plants. It doesn't affect Excel and the like in the same manner.


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## BulletToothBoris (Jan 17, 2013)

Thanks for the good input. I guess I'll just conclude that an airstone does not disturb natual baseline dissolved CO2.


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## kman (Dec 11, 2013)

BulletToothBoris said:


> Thanks for the good input. I guess I'll just conclude that an airstone does not disturb natual baseline dissolved CO2.


That would be my conclusion as well, based on what I know about pressurized gasses.


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