Biologically ideal magnesium supplement for reef aquariums. A sufficient supply of magnesium is as essential for the growth and well being of reef building coralline algae as calcium. It is one of the major constituents of seawater and is directly involved in algae photosynthesis, I.E. the conversion of carbon dioxide (CO2) and light into organic compounds. The addition of plain magnesium salt, however, is not sufficient and interferes with the ionic balance of the tank water. Tropic marin bio-magnesium creates a natural environment in the aquarium and delivers magnesium in a natural biologically available ionically balanced form.