CO2 and KH


thank you for your comments. I agree 100% with what you write, but one 
question hasn't been answered yet:

is the ammount of CO2 needed (as in bubble rate or 'how fast does my CO2 
bottle empty') to hold a dissolved CO2 concentration of 18 mg/l the 
same in 

-water with a KH of 10 
-water with a KH of 4 ???

assuming one doesn't care about the difference in resulting pH and all
other factors (temperature, surface motion, plant consumption etc.) being
the same. I wrote 'hold' that CO2 concentration, because additonal CO2
would be produced, of course, by titration with acid to bring down KH. As
you have explained in your post. We will see. The opinions here at the lab
at work still differ. I've already started to put some acid (acetic)
_slowly_ into my aquarium. So far no adverse effects. It's nice to see how
the pH drops initially and then slowly recovers as the excess CO2 leaves
the water. I preferred the acetic stuff, because the acetate will get
metabolized, as opposed to the Cl- ions of hydrochloric acid. It's also