Two Little Fishies Kalkwasser 500 g (1.1 lb.), Calcium Supplement Mix. Use to supply calcium and alkalinity without disturbing the ionic composition of seawater. Our pure source of Calcium Hydroxide makes the ideal solution for replenishing calcium and maintaining alkalinity, for corals, clams, and calcareous algae that build skeletons of calcium carbonate. Promotes growth in corals and calcareous algae. It also helps maintain pH, precipitates phosphates and enhances protein skimming. Precipitates phosphates and some heavy metals from water. Enhances protein skimming.Made from a pure grade of calcium hydroxide.Detailed instructions for use on bottle.