Just for info (Hanns-J Krause CO2 Test)
Hanns-J Krause CO2 Test
Author Handbook Aquaria Technology
Krause recommends a different method to measure CO2 content. That method is insensitive to the presence of unusual buffers
(peat, acid, alcali etc)
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.
Step 1: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 (around 0.5 to 0.6ppm).
—>Measure pH of the water (=X).
Step 2: Next exhale through a pipe into the water sample for 2 or 3 minutes. The concentration 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:
optimum pH = 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.