High-purity powdered magnesium blend, 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 to form skeletal material, Stronger and more economical than liquid magnesium solutions; created for hobbyists maintaining multiple reef aquaria, Formulated by a marine scientist, Powder, 300-g, SKU: RYLHC1010