Reef Foundation Products are balanced supplements for building robust coral skeletons. Ensuring that the basic foundation elements, Calcium, Magnesium, Strontium and Carbonate are readily available in your tank in the correct biological ratio encourage the robust coral skeletons that are essential for all reefs. Reef Foundation products provide a complete solution for supplementing these foundation elements. Making sure all types and sizes of reef are well supported. Reef Foundation C is a blend of Magnesium salts. Powder supplements are recommended for aquariums above 500 litres (125 gallons). 1g of powder C will raise the Mg level of 100 litres by 1ppm.