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Testing for CO2 in water

I've been referring others to the following site (which another member kindly 
referred me to when I was looking for a *formula* of sorts while filtering 
with peat) for help in determing CO2 levels/ph and had difficulty due to 
buffering, etc. Any type of buffering can render the basic charts inaccurate.

I would appreciate if others already successfully injecting CO2 could 
evaluate the following formula and see if it is, indeed, accurate with 
respect to pH levels in their own tank water. This could be immensely helpful 
to those reading and having difficulty determining bubble rate/CO2 level/pH 
and finding results from charts and CO2 tests questionable.

This is posted at the Krib. Thanks for your help.


 <A HREF="http://www.thekrib.com/Plants/CO2/co2-meter.html">A Cheap CO2 Meter<

<<<Krause describes a method in his book on aquarium water that is supposed to
work with any kind of water. Not absolute pH is the key, but the change of
pH by two units is used to determine correct CO2 concentration.

Take a sample of your water and aerate it for some time until all CO2 is
removed. In that case the concentration of CO2 is in equilibrium with 
the surrounding air (0.6ppm). Measure pH of the water (=X).

Next exhale through a pipe into the water sample. After a while the
of CO2 in the water will assume 60ppm. Measure  pH of the water (=Y).

The optimum CO2 concentration of 10-20ppm is at the pH value about 2/3 of 
the difference between X and Y: pH,opt = X +.67*(Y-X).

This will work even with buffered water, although the change in pH might be
small and only detectable with an electronic pH meter.>>>