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 C contains blended salts of Magnesium and is part of Red Sea's complete Reef Care system. 1 ml of Reef Foundation C will raise the Mg level of 25 gallons of water by 1 ppm. Includes a convenient measuring cup for easy dosing.