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Does an airstone force the CO2 out of your water?

Saint Paul, Minnesota USA 20g Freshwater Started June 10th 2008
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Hi,
Actually, it depends up on the situation in the tank.

IF you have a "regular Ole Aquarium" with some fish, some
plants, and an air-stone, then NO, the air-stone is not
forcing CO2 out of the tank. It is increasing the O2
saturation by riling the surface, cycling water to the
surface, and exposing small bubbles of air to the water
as it rises to the top where they burst. As the water is
in contact with the bubble it is absorbing the O2.

In ambient circumstances the normal saturation of CO2, is
about 5 mg/l.

Now, if you have an aquarium with fish and plants and you
are injecting CO2 into the tank to aid plant growth, then
in general, you do not want to rile the surface. Filter
returns are kept under the surface so they do not rile the
surface or splash. In other words you want to maintain the
surface tension so that the excess CO2 (the gas saturation
above the normal 5mg/l) does not escape into the atmosphere.
Generally, with CO2 injection of any kind
(DIY or Bottled) you want to maintain a saturation between
15mg/l and 30mg/l. If you toss in an air-stone then you
are forcing the tank to get rid of the excess CO2 and return to normal levels.

If you are using DIY CO2 injection, every bit of it counts
and you don't want to do anything to drive off the CO2
build up in the tank. So, with DIY there should be no air
stones, and no filter splash, nothing that breaks the surface
tension.
If you are using bottled gas you can use an air-stone if
you need/want to, and you can have filter splash as
maintaining the surface tension is not that important.
With bottled gas, you can always turn up the rate of
injection to overcome any losses.

Does that help?

Frank


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