Oceanlife Calcium Pearls is a granulated natural calcium with a purity of 99%, ideal for use in calcium reactors. It can also be used as substrate in marine aquariums or biotopes of Lakes Malawi and Tanganyika. Particle size: 9-12 mm. Corals needs calcium, magnesium and many other elements to grow. These elements can be added to the system using a calcium reactor. Oceanlife reactor media are very pure, with no pollutants. 1000ml