Reef Endurance Bulk Calcium Chloride 30lbPharmaceutical Grade Calcium Chloride Aquarium Supplement Reef Endurance Calcium Chloride is a pharmaceutical based aquarium supplement that mixes crystal clear with no unwanted impurities. In reef aquaria, maintaining calcium within a range of 412 450ppm will enable corals and other reef building invertebrates to proliferate. For best results, use in conjunction with Reef Endurance Sodium bicarbonate or Soda Ash as a two part balanced regimen.