Reef Foundation® C A magnesium complex for balanced formation of coral skeletons. 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 positive coral health and growth. Red Sea's Reef Foundation C contains blended salts of magnesium and is part of Red Sea's complete Reef Care Program. 1ml will raise the Mg level of 100 liters (25gal) by 1ppm.