Red Sea's Reef Foundation Complete Supplement Pack contains all five of the essential foundation elements required in order for corals to thrive within the reef aquarium. Unlike the natural reef where there is an immense reservoir of foundation elements, in an aquarium these elements are constantly depleted due to coral growth and other biological activities. Therefore, calcium, carbonates (alkalinity) and magnesium require regular testing and supplementing. The Reef Foundation Liquid Supplement Pack is part of Red Sea's complete Reef Care Program, which provides all of the supplements, test kits and coral foods required in order to maintain a successful and healthy coral reef aquarium.