You should use the initial pH reading because that is what you really interested in. The CO2 level that is in the water at the point of time.IUnknown said:I am using The Lamotte 4491 Alkalinity test kit to measure KH in my aquarium. I am using the results to measure the Co2 in the system using the following calculator and a pH probe,
My problem is that I initially get a reading, and then the color changes as I let the sample sit (as if the Co2 is being gassed off, and my result changes). What I want to know is if I should use the initial reading to determine my Co2, or should I let the sample sit for an hour to measure my Co2?
Also, Chuck's webpage describes PO4 concentrations as a problem. I was wondering at what levels do they become a problem. I maintain 2ppm throughout the week.
IME, PO4 levels can vary widely without causing problems to a system where CO2, K and NO3 are well maintained. The levels in my tank varies from 0.5ppm to 30ppm at different stages (including a period where I made a boo-boo in dosing PO4) without causing problems.