Highly-concentrated ionic magnesium solution, 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, Stronger than most competing products, Contains no unwanted organic material such as EDTA, gluconate, or polygluconate, Formulated by a marine scientist, Liquid, 500-ml, SKU: RYLHC1052