Seachem Reef Advantage CalciumSeachem Reef Advantage Calcium is a non caustic (pH 8. 3 8. 6) optimized blend of ionic calcium designed to restore and maintain calcium levels to those found in natural seawater. Note that if either calcium or carbonates become deficient, coral growth will cease, followed by a rapid decline in coral health. Raises calcium to natural seawater levels Capable of raising 20 gallons of water by 25 ppm of calcium with only 1 teaspoon Non caustic and pH