In a non-Co2 injected tank, does an Airstone gas off Co2, or pull it in?

Rocketman

Rocketman

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A few days ago, DJLen said:
In a non-injected tank CO2 will be added to the tank through gas exchange by aerating the tank and good water movement. Keep in mind that the CO2 concentrations in a non-injected tank are quite low 'Gassing off' occurs in CO2 saturated water. Aerating it will actually draw gas into the tank from the atmosphere(minimal though it may be).
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I wasn't sure about this, it just seemed like it removed a long-standng belief that every fish tank should have an Airstone. THe rest of what I planned putting here can be found in another thread: http://www.aquariacentral.com/forums/showthread.php?s=&threadid=14382

Mostly, the meat of it is that every beginner has an airstone. Does this mean that they shouldn't have one?
 
To answer your question directly - it pulls it in.

But that depends on a few things. If you're not injecting CO2, the levels of CO2 in the water depend on how much it can absorb from the air. So the airstone helps. But fish also release CO2 into the water as they breathe. So with a full fish-load, your CO2 levels could actually be higher than atmospheric. In this case, an airstone would cause that excess CO2 to be released into the atmosphere.

It has been my recommendation to always have surface agitation in a non-CO2-injected tank. Since plants aren't growing at vigorous levels, they aren't producing as much oxygen as the fish might need. The tank will also be much more stable and consistent with an airstone, HOB filter or other form of surface agitation.
 
So a tank that is slightly under-stocked with a Canister Filter setup, (to produce low surface agitation,) such as mine would make use of an airstone.

But one more question for you all. I added Flourish Excel, (the "liquid Co2.") Now what?
 
Good, Good. I don't want my plants to grow that much, (I am sometimes away from home for a week at a time,) I just want them to stay alive. I honestly couldnt care if they don't grow one inch next year...All I have now are an Amazon Sword, Bacopa, and some Anacharis, (which I don't think will work out,) along with some, (8 stems) of Ludwigia. Do you think this setup would support one or two more Swords? There is a large empty spot in the tank now where the Hornwart used to be. I'm deciding what to put there.
 
And the lighting is only .5 WPG.

But I use Aqua-Glo, which are supposedly get spectrum.
 
Rocket Guy, the simplest way to put it is if the atmosphere has more CO2 in it than your water table, an air stone will draw CO2.
If the water table has more it will gas it off.
I do agree with the Gulf guy that in your circumstance an air-stone would be beneficial.
I do not believe that "every tank should have an airstone". In an injected tank they defeat the purpose.
Len
 
If the crabby old fish keeper can chime in, it will be a cold day in Sao Paulo when I have any fish tank with an airstone.

Do you have a filter? What makes you think that you (or anybody) need(s) an airstone? That usage dates back to the daye of small plastic box filters (air-driven of course).

With current technology, there is no excuse other than personal aesthetics for use of an airstone.

But whether or not such a device removes or adds CO2 does depend on the kinetics of the particular tank, as has been said. If the tank is lower than air-equilibrium for CO2, it will bring some CO2 in. If the tank is greater than air-equilibrium for CO2, it will blow some CO2 off. Individual tank parameter - if you can't test at that level, you will never know.

Blowing off CO2 to control plant growth is not a very good idea - the algae however will love it. With sufficient carbon (i.e., CO2 for most plants), the plants will use nutrients. Lacking CO2, they will stop growing and use less nutrient. Excess nutrients with insufficient carbon results in? This is a test. ;)
 
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