High Purity Magnesium Media for Placement in Reef Aquarium Media Reactors Overview High-purity, magnesium-rich mineral that may be employed in traditional calcium reactors, or even blended in to pre-existing aquarium substratum, to gradually increase and maintain the magnesium concentration in the system. 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. Composed of magnesium, calcium, and carbonates. Optimal average particle size for use in media reactors and calcium reactors. Free of chloride and sulfate. Mined in the United States.