Calcium supplement
Why is calcium required? Calcium is a major constituent of calcareous algae, skeletal material of hard corals and the skeletal needles of soft/leather corals. Calcium also fulfils many biological functions.
These processes result in depletion of calcium. Quite often a too low calcium concentration retards growth of corals and calcareous algae. NSW (Natural Sea Water) contains 400 - 450 mg/L calcium. This is also the value we should strive for. For a stable aquarium environment the fluctuation in calcium content should not be more than approx. 15 mg/L.