Calcium, Magnesium, Strontium and Carbonate are the basic foundation elements of coral skeletons. All of these elements need to be available in balanced proportions for coral health and growth. Reef Foundation A contains blended salts of Calcium and Strontium in the ratio required by corals, and is part of Red Sea's complete Reef Care System. 1 ml of Reef Foundation A will raise the Ca level of 25 gallons of water by 2 ppm. Includes a convenient measuring cup for easy dosing.