Magnesion Liquid Reef Supplement by Brightwell Aquatics is a highly-concentrated ionic magnesium solution. Magnesion provides magnesium, which helps regulate the balance between calcium and carbonates in aquarium water, and is a component of aragonite, the mineral secreted by reef-building organisms such as corals, clams, and their allies to form skeletal material. It contains no unwanted organic material such as EDTA, gluconate, or polygluconate. Stronger than most competing products. Formulated by a marine scientist.