The Fritz RPM Elements Magnesium Aquarium Water Treatment provides biologically useful forms of magnesium to support a healthy aquarium. This magnesium is used in the growth and development of many corals， invertebrates and helpful algae. It plays a key role in helping to maintain the balance between your tank’s calcium and alkalinity. This treatment includes the highest purity magnesium chloride and magnesium sulfate in a balanced ratio， helping to maintain the ratio that’s found in natural seawater.