1 kg = 27.43 €
The total hardness is a value of the amount of alkaline earth metals. These metals - especially calcium and magnesium - are essential minerals and must therefore always be present in sufficient quantity in the aquarium water. In fresh water aquarium the consumption of calcium and magnesium is very low, so it is possible to enrich the total hardness only by doing a regularly water change.
In the marine aquarium especially coralline algae and gorgonians require magnesium for healthy growth. The natural magnesium content of the oceans is about 1300 to 1400 mg/l. If magnesium goes below this concentration, it can happen that the calcium consumption increases extremely. Thus, if the calcium reactor provides sufficient alkalinity, but the calcium concentration in the aquarium falls steadily, this may be a sign of magnesium deficiency. Check in any case, the magnesium concentration and correct them if necessary with the Aqua Care products Magnesium / GH plus or Super-Magnesium.