The JBL ProAqua Test KH Carbonate Hardness is an easy to use quick-test for determining the carbonate hardness or the antacid capacity of saltwater and freshwater. It corresponds thereby to 1 drop = 1dKH.Why test? Depending on its origin, and often due to the nature of the subsoil, water can contain different amounts of various mineral salts. Most of the salts dissolved in it are alkaline earth and alkaline hydrogen carbonates. Together with carbonates and carbon dioxide (CO2), hydrogen carbonates form an important buffer system that prevents dangerously high pH fluctuations in water. The carbonate hardness (KH) measured provides the total concentration of hydrogen carbonate in the water and can therefore in rare cases (when alkali hydrogen carbonates are mainly present, e.g. in East African lakes) be higher than the general hardness, which only takes into account the alkaline earth salts. Most freshwater fish and plants in the aquarium can be kept successfully with a carbonate hardn