Fluval Sea Calcium is a concentrated form of calcium that is easily absorbed by corals and other invertebrates for a strong skeletal structure, while not affecting the delicate ionic balance in marine aquariums. Regular dosing is strongly recommended to offset constant depletion by coral, coralline algae and other invertebrate growth. Fluval Sea Calcium is provided in the form of Calcium Chloride, a preferred compound as chloride is the most common ion found in marine water and inherently this will avoid unbalancing ionic ratios. Fluval Sea Calcium supplement uses only USP grade calcium chloride. This ensures pure product and the absence of any unwanted contaminants.