Seachem Reef Advantage CalciumÃ¢â€Â¢ is equivalent to dry Reef CompleteÃ¢â€Â¢. It is a non-caustic (pH 8.3-8.6) optimized blend of ionic calcium designed to restore and maintain calcium to levels found in natural seawater. Calcium and carbonates are essential to all coral growth. If either becomes deficient, coral growth will cease, followed by a rapid decline in coral health. Reef Advantage CalciumÃ¢â€Â¢ also includes magnesium and strontium in amounts proportionate to typical utilization ratios (100:5:0.1, Ca:Mg:Sr). This allows one to maintain these two important elements while maintaining calcium. If either usage or precipitative loss results in a more rapid loss of either magnesium or strontium, then Reef Advantage MagnesiumÃ¢â€Â¢, Reef Advantage StrontiumÃ¢â€Â¢, or Reef StrontiumÃ¢â€Â¢ may be employed. Unlike limewater (kalkwasser), Reef Advantage CalciumÃ¢â€Â¢ does not have a caustic pH and will not deplete magnesium. Used as directed, it will not deplete alkalinity. 500 g treats 16,000 L (4,000 gallons).