Highly-concentrated ionic calcium solution. Increases the concentration of calcium in marine aquarium water to provide corals and other reef-building invertebrates with one of the most important elements required for growth. Is ionic rather than chelated, and contains no unwanted organic material such as EDTA, gluconate, or polygluconate. Over 50% stronger than most competing products. Free of phosphate, silicate, and organic material. Formulated by a marine scientist.