ESV Calcium Chloride is a very pure anhydrous grade free of phosphates and nitrates. The advantage of using Calcium Chloride as a calcium supplement in marine aquaria is its very high solubility in water. This property allows the aquarist to rapidly adjust calcium concentrations to desired levels. The aquarist should be aware that Calcium Chloride does not add bicarbonate and carbonate ions to the system. Since most calcifying organisms require these ions in addition to calcium ions, the aquarist should monitor the alkalinity frequently when using Calcium Chloride and make the proper adjustments with a buffer additive. Calcium Chloride can directly reduce alkalinity by elevating the calcium ion concentration to excessively high levels and thereby initiate the precipitation of calcium carbonate from the water. This may or may not be visibly detectable, depending on the magnitude of precipitation.