Increases carbonate hardness (KH). Concentrated (4000 mg / L). Does not deplete calcium. Reef Carbonate is an exclusive blend of concentrated salt (4000 meq / L) designed to restore and maintain alkalinity in the reef aquarium. As well as supplying carbonates, it maintains calcium levels. If either becomes deficient, coral growth will cease, followed by a decline rapide in coral health. To avoid this, you need to supply carbonates (Reef Carbonate) and calcium (Reef Advantage Calcium or Reef Complete).