Reef Crystals 4kg are an enriched sea salt mixture, contains a supplementary dose of calcium, vitamins and selected trace elements. Developed specifically for use in refined reef tanks, it was the first widely available reef salt mixes. The introduction of important compounds at higher concentrations than in natural seawater ensures longer availability of the substances assimilated and quickly used up in a flourishing reef aquarium. A special additive helps to eliminate surplus heavy metals, like copper, which are often found at excessive levels in flourishing reef aquariums. Each batch is analysed to guarantee its composition and uniformity.