Fluval Sea 3-Ions Supplement is a concentrated blend of 3 essential ions–calcium, magnesium and strontium–at proportions that maintain optimal ionic balance. By raising and maintaining optimal levels of calcium, magnesium and strontium, this supplement supports coral growth and helps keep marine aquariums naturally stable. Fluval Sea 3 Ions contains USP (Pharmaceutical) Grade calcium chloride, magnesium chloride and strontium chloride, ensuring that you're getting a high quality and ultra pure product that's free of unwanted contaminates. It does not contain gluconates, nitrates, phosphates. Fluval Sea 3-Ions Supplement is strongly recommended for offsetting ongoing depletion caused by coral absorption, coralline algae and organic compounds.