Hello,
May I know why you need more precise KH reading than the typical test kit provided ?
I had tried Dupla, Sera and Tetra before and they all work about the same by counting the drop into a fixed sample volume that turn from blue to yellow. That is generally good enough for determining teh CO2 level (combining with the PH reading).
By the way, I learnt from the APD mail list that the common KH-PH-CO2 table (that available in many reference source) only apply to a tank water where the bicarbonate is the main buffer of the water's alkalinity. If there are other staff in the water (such as PO4 due to e.g. too much fish food) than it may gives a false reading.
One way to "calibrate" the reading is to take some tank water in an opened container and leave it overnight at a opened area (to allow its CO2 level equalize with the atmoshoere level of ~3ppm CO2) then check the PH of this sample water and from the KH-PH-CO2 level find out what would be the KH reading giving the PH reading you measured and at 3ppm CO2, this will give you a reference KH number. Then use this reference KH number and the tank's PH level to find out the "real" CO2 level of the tank. This method will remove the factor due to the other staff in the water than affect its KH value other than the effect by the bicarbonate.
Bookmarks