| As far as filtering the CO2, any amount of surface disturbance, aeration, or other churning of the water will serve to balance CO2 levels with what's in the air. Because of this, adding CO2 to a river setup likely won't do much. The CO2 concentration will be higher in the water than in the air, and so diffusion will bleed the excess CO2 into the air.
Conversely, if you have plants and don't add CO2, the plants will continually be absorbing CO2, thus putting the CO2 concentration lower in the water than in the air, and diffusion will work to raise the CO2 up.
Am I making sense? (I understand the process, but I have problems explaining it... I'll try again if I'm being confusing.) |