It is recommended that calcium and magnesium concentrations in the aquarium system be determined by using accurate test kits prior to supplementing. Do not add this product directly to an aquarium containing live animals without first diluting in water as directed. Technical Background: This method of calcium and carbonate supplementation is advantageous to hobbyists interested in a simple and effective means of providing elements and molecules required for skeletal growth of reef-building organisms such as corals, clams, and their allies. The magnesium concentration in all reef aquaria should be adjusted to, and maintained between, 1,290 - 1,320 ppm before using these supplements (alone or together) or other calcium and alkalinity products. Doing so helps prevent unwanted precipitation between calcium and carbonate ions. Additional information on this subject is available on our website and on the label for Brightwell Aquatics Magnesion. The rate at which calcium and carbonates are extracted from the water is determined by the stocking density of reef-building livestock, type of lighting, and other conditions; therefore, each aquarium will have different requirements for the rate of supplementation.