JBL ProAqua Test GH General Hardness for fast, reliable and accurate determination of the total hardness in fresh water. 1 drop corresponds to 1 °dGH. Color change from red to green.

Why test? Depending on its origin, and often due to the nature of the subsoil, water can contain different amounts of different mineral salts. By definition, general hardness is the total concentration of all alkaline earth ions in water. The general hardness is mostly formed by calcium and magnesium salts. Most fish and plants can be kept successfully with a general hardness of around 8-25 °dH.