Seachem Reef Calcium  is a concentrated (50,000 mg-L) bioavailable polygluconate complexed calcium (phew!) intended to maintain calcium in the reef aquarium without altering pH (formulated at 8.2). Polygluconate complexation confers several benefits: it increases bioavailability of the calcium, it provides a rich source of metabolic energy to help maintain peak coral growth, and it inhibits calcium precipitation-alkalinity depletion. One side benefit includes enhancement of denitrification. Polygluconate contains no nitrogen or phosphorous, thus it is biologically impossible for it to lead to algae growth in a well maintained reef system. Reef Calcium may used alone to maintain calcium but will provide enhanced levels of coral growth when used in conjunction with an ionic calcium supplement (Reef Complete, Reef Advantage Calcium, Reef Kalkwasser). Reef Calcium is intended to maintain calcium levels ; if calcium becomes seriously depleted one should either perform a water change or use an ionic calcium supplement to restore the depleted level of calcium. A 100 ml bottle treats 1,600 L (400 gallons).