One of the members of Tom Barr's site did some testing of outgassing of tank water recently. He found that even after 48 hours the pH was slowly rising, indicating either that evaporation was raising the KH or that CO2 continued to outgas. As a result, I tried some testing to see if you could reach a stable pH by blowing into a water sample for a reasonably short time. It appears that you can do so if you blow bubbles in the water for 5 minutes or so. That suggests another awkward, inconvenient way to test for CO2, but it is still going to be a very crude measurement. I think the basic problem is that the ppm of CO2 depends on an exponential - ten raised to the power of a pH difference. And, that really compounds errors in measuring pH for any reason.
I have decided that for now I am just going to use the maximum amount of CO2 I can without distressing the fish too much. |