Red Sea 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 complete reef care system. 1-mL of reef foundation C will raise the magnesium level of 25-gallon of water by 1 ppm. Includes a convenient measuring cup for easy dosing. Available in 500-ml bottle.