Test Kits & Equipment » Hardness Tests

General Hardness is primarily the concentration of the Calcium (Ca++) and Magnesium (Mg++), the two most important metal cations with more than single positive charge. If the amount of these salts is low, then the water is called soft.

When their amount is higher, the water is called hard.

Total hardness is normally given in German degrees (dH°), whereby 1 dH° is equal to 10 mg/Lt dissolved Calcium oxide. The concentration of these salts inside the water effect the biological functions of plants and fishes.

The optimal value for the General Hardness depends on the species of fish and plants. Where many African and South East Asian species flourish in relatively hard water, South American ones may need soft water. By the way, if a range of hardness of 3 to 16 dH° is accepted, a range of 4 to 10 dH° is considered to be ideal.

The periodical analytical valuation of GH in the aquarium water should be considered by the serious aquarium enthusiast.