Re: Oxygen saturation concentration

Paul Sears responded responded:
>> Imagine an aquarium with half of the surface exposed to air and half
>> exposed to CO2. In this case the average atmosphere above this tank is 50
>> percent CO2, 10 percent O2, and 40 percent N2. Obviously the partial
>> pressures of N2 and O2 will be reduced.
>        This is not a "mixed gas", though.

Yes, quite true! But it is a very similar situation to an aquarium with a
CO2 reactor.

>> In this case since a continuous transport of the the gases from one
>> atmosphere to the other will be established the partial pressures in the
>> liquid will also be affected by how efficiently each gas diffuses
>> into/outof the liquid, I don't know if different gases have different
>> diffusion rates into a liquid or not, however I suspect so, since this is
>> "sorta" how a gas chromatograph works.
>        The point is that it is a very complicated situation!

I'll agreee with that!
>> Anyway not to worry, the partial pressures of CO2 that we are using are so
>> low that not much O2 or N2 leaves.
>        There is another little wrinkle to this.  If you cover your tank
>well, you could get CO2 buildup under the cover.  I think it
>would be difficult to do this well enough to cut the O2 concentration
>at the surface of the water, but it _could_ be done.
>        What are plants for anyway?

Actually if the CO2 input from the fish and CO2 injection matched the plant
usage the atmosphere above a sealed but vented tank (we don't want it to
explode) would eventually become O2 and CO2 with the addition of whatever
N2 was added in the fish food but not utilized by the plants. This assumes
that the plants are growing and fixing more carbon then they are releasing.
Who knows what the effect on fish and plants of an O2 and CO2 atmosphere
would be?