Thrive Calcium is designed to increase calcium levels in your salt water reef aquarium. Most reef aquariums will need supplementation of calcium for inhabitants like coral to grow and to multiply. Thrive Calcium is a saturated solution of calcium chloride. Thrive Calcium is the most concentrated and efficient Calcium product on the market. Stony corals use calcium in combination with carbonate and strontium to form their skeletons. Soft corals use calcium to form sclerites that strengthen their base. Some algae such as coralline also use calcium to form.