GH & KH test Aquarium Pharmaceuticals
For testing GH and/or KH levels of the aquarium water. Suitable for freshwater.
Tests tap water and freshwater aquariums for general hardness (GH) and/or carbonate hardness (KH).
Rapid pH crashes are usually due to a too low carbonate hardness (<1-2 ºkH), combined with the presence of some acid accumulation (for example if you add CO2 or from nitrification). In the same way, a too high carbonate hardness may difficult the pH to come down to the desired level.
It's also important to check and control general hardness, which monitors divalent cation levels (Ca2+ and Mg2+ being the most relevant); this cations are related to fertility and proper immune function of mucose, amongst other issues, and should be fitted to those prevalent in natural habitat of the fish.