Salifert Calcium Test Kit (Reef)Calcium is a major constituent of calcareous algae, skeletal material of hard corals and the skeletal needles of soft leather corals. Calcium also fulfills many biological functions. Quite often a too low calcium concentration retards coral and calcareous algae growth. NSW contains 400 450 mg L calcium. Which is also the value we should strive for. For a stable aquarium environment the fluctuation in calcium content should preferably not more than