Magnesium supplement for balanced formation of coral skeleton. 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 MAGNESIUM contains blended salts of magnesium and is part of Red Sea's complete Reef Care Program. Liquid supplement: 1ml will raise the Mg level of 100 litres (25 gal) by 1ppm.