"David Wee" wrote in message
...

Another thought:

It seems that one can achieve a maximum CO2-water diffusion *rate* with a
powerhead/filter intake + bubble system, but retention of the CO2 will be
based on the water chemistry (pH, kH, not clear on this, but indeed it
seems chemically related).

check out http://www.csd.net/~cgadd/aqua/art_plant_co2chart.htm

Assuming no other buffering ions... there is a direct relationship between
pH, KH and CO2. Chuck Gadd has a calulator ... "The formula used for this
calculation is: CO2 (in PPM) = 3 * KH * 10( 7-pH ) where KH is Carbonate
Hardness in degrees. " The (7-pH) is an exponent, the formating got lost
in the cut and past.

I don't think water chemistry has anything to do with CO2 retention. That
is controlled by somebody or other's laws (hey it been 30 years since
college) that govern diffusion and etc.

Bob