Liquid organic calcium source. Accelerates coral growth. Reef Calcium is a concentrated product (50,000mg/L) designed to maintain calcium levels in reef aquariums without affecting pH. It contains no nitrogen or phosphorus, and therefore does not cause algae growth. Additionally, it contains organic calcium instead of ionic calcium, so coral expends much less energy to assimilate it. Reef Calcium is intended to maintain calcium levels and coral health. To speed up growth, it is best used alongside an ionic calcium supplement. 500 ml treats 8000 l.