Instant Ocean Reef Crystals is formulated specially for use in reef aquariums. The enriched formulation provides optimum effectiveness. Reef Crystals contain essential ocean reef elements in concentrations greater than those found in natural sea water. Extra calcium, vitamins and other trace elements help ensure vigorous growth and survival of corals, anemones and other invertebrates in a captive environment. Also contains metal detoxifier to neutralize traces of heavy metal often present in domestic water supplies. The 2.8 pound box makes 10 gallons of reef salt water.