CO2 Tables -- or - How to save money on CO2?

["S. Hieber" <shieber at yahoo_com>]

Two formula are profferred for calculating CO2 levels from KH and pH
values -- there might be more but I only know of two (not counting
algebraically equivalent recastings):

12.839*KH*10^(6.37-pH)


15.664*KH*10^(6.37-pH)

For an example, at a KH of 5.5 and a pH of 6.8, the former formula
indicates a CO2 level of 26 ppm, while the latter llisting indicates a
level of 32 ppm.  If your aquarium was running at either 26 or 32 ppm
of CO2, I doubt that you would see much difference in plant growth --
especially given all the other things that affect plant growth.

Still, I am disinclined to call the difference in CO2 values negligible
or insignificant; it's roughly a 20% variance.  That's okay for budget
work but one expects chemistry to be a bit more precise.

I have read some aquatic gardeners' complaints that the tables must be
wrong because the useful levels of CO2, in practice, are much
higher/lower than the table indicates.  This could be due to any of
several factors.  Perhaps one of the factors is using an slightly
inaccurate chart.

Anyone care to reconcile the differences or point out my misreading of
the formulas?

I suspect that, at most, only one of the formulas is correct.  I am
curious which.  Maybe one should pick the chart that saves the most
money  on CO2  ;-)

Scott H.

__________________________________________________
Do You Yahoo!?
Sign up for SBC Yahoo! Dial - First Month Free
http://sbc.yahoo.com