Magnesium pro Additive for the Calcium reactor for the increase of the Magnesium contents. In the marine water aquarium, a great quantity of Calcium and Magnesium is required in order to achieve an optimum growth of corals and red calc algaes. By the normally used materials in the Calcium reactor, the Calcium content will be more increased than the Magnesium content. By admixing of up to 10% Magnesium pro into the used material, there will continuously befed Magnesium and the Magnesium contents in the aquarium is stabilized. Available in 1000g, 3500g.