Re: NANFA-- CO2? - Fill your planted tanks with mudminnows or anabantids!

Bruce Stallsmith (
Sat, 20 Jan 2001 15:48:20 -0500

True, HCO3- and CO2 are in equilibrium, but _not_ one to one correspondence.
Around pH 6-7, CO2 is the dominant species. As the pH increases past 8 to
about 10, CO2 falls out of the picture and HCO3- becomes dominant; this pH
range is what one would find in a freshwater pond about 1:30 pm on a hot,
sunny July or August day in North America as the result of photosynthesis
removing the CO2 from the water. By evening in such a pond, the pH would
have typically fallen back to around 7 as photosynthesis slows down enough
so that CO2 can dissolve into the water faster than photosynthesizers will
use it, so the equilibrium makes a pronounced shift. Such a pattern probably
happens in many planted, well-lit aquaria although maybe not as sharply;
most aquaria are managed in such a way that pelagic photosynthesizers are
kept to a minimum, i.e. we don't usually like "green water" tanks.

--Bruce "better living through chemistry" Stallsmith
Huntsville, AL

>Subject: Re: NANFA-- CO2? - Fill your planted tanks with mudminnows or
>Date: Sat, 20 Jan 2001 14:11:54 -0600
>On 19 Jan 2001, at 16:55, Bruce Stallsmith wrote:
>If I remember the chemistry of this correctly, HCO3 and CO2 are in
>equilibrium in water. The direction of the equilibrium depends on
>KH, pH, and temperature.

Get your FREE download of MSN Explorer at

/"Unless stated otherwise, comments made on this list do not necessarily
/ reflect the beliefs or goals of the North American Native Fishes
/ Association"
/ This is the discussion list of the North American Native Fishes Association
/ To subscribe, unsubscribe, or get help, send the word
/ subscribe, unsubscribe, or help in the body (not subject) of an email to
/ For a digest version, send the command to
/ instead.
/ For more information about NANFA, visit our web page,