Reef  magnesium is a concentrated (80,000 ppm) optimized blend of magnesium, chloride, and sulfate salts designed to restore depleted levels of magnesium with minimal impact to the ionic ratios found in natural sea water.Magnesium plays a vital role in reef aquaria: it helps maintain calcium and carbonate (composing the majority of measurable alkalinity)concentrations by limiting unwanted inorganic precipitation with each other. In the absence of adequate magnesium ions, calcium and carbonate ions bond rapidly, depleting their concentrations in the system and creating the false impression that heavier supplementationis required to re-establish the desired concentrations.