Red Sea Reef Foundation C MagnesiumCalcium, 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 Seas MAGNESIUM contains blended salts of magnesium and is part of Red Seas complete Reef Care Program. Further information can be found on Red Sea's website: Click here See our Return & Refund Policy here