Reef Basis Cal React is a supreme quality, calcium rich aragonite, specially selected for for use in calcium reactors. It provides a gradual increase in calcium and carbonate levels to support both calcium level and buffering in the aquarium. It is free of chloride and sulfate and will not contribute to ionic imbalance in the system. Controlled dissolution of aragonite in a reactor vessel is one of the most effective and preferred methods of increasing and maintaining calcium levels and alkalinity in a reef aquarium. Cal React provides calcium, as well as other minerals that are present in aragonite, such as strontium in a gentle release over time, allowing for increased stability of both the calcium and carbonate levels in the aquarium. Continuum recommends that you maintain a calcium level of 410 to 440 ppm in a reef aquarium.