All calcareous animals, especially corals, need calcium to grow and flourish. However, the growth rate of corals depends mostly on the algae that live symbiotically within them as this algae uses carbon dioxide (obtained from certain calcium compounds present in natural sea water) during photosynthesis, making the calcium freely available for the coral to absorb. Only when calcium and carbon dioxide are available together can this symbiotic relationship work, and Tropic Marin Bio-Calcium is the ideal source of both.