Reef Carbonate is a concentrated (4,000 meq/L) optimized blend of carbonate and bicarbonate salts designed to restore and maintain alkalinity in the reef aquarium. Calcium and carbonates are essential to all coral growth. If either becomes deficient, coral growth will cease, followed by a rapid decline in coral health. To prevent this you must provide carbonates (Reef Carbonate) and calcium. Used as directed, Reef Carbonate will not deplete calcium, magnesium, or strontium which usually tend to precipitate with increasing alkalinity. Reef alkalinity should be maintained at 3-5 meq/L (8-14 dKH) and alkalinity should not be allowed to fall below 2 meq/L. 500ml.