Concentrated ionic calcium powder supplement. Maintains magnesium and strontium. Can be added directly to the aquarium. Reef Advantage Calcium is a non-caustic (pH 8.3-8.6) blend of ionic calcium designed to restore and maintain calcium to levels found in natural seawater. Calcium and carbonates are essential for all coral growth. If either becomes deficient, coral growth will cease, followed by a rapid decline in coral health. Reef Advantage Calcium also includes magnesium and strontium in amounts proportional to typical utilization rates (100: 5: 0.1 / Ca: Mg: Sr) and helps maintain these two important elements while maintaining calcium levels. 4 kg treats 128000 l.