Strontium is an important trace element that aids in the calcification process of reef-building corals and calcareous algae, and is essential to ensure the optimal health and vitality of all calcareous reef inhabitants. Although typically contained in most salt mixes, strontium is rapidly depleted in the average reef system, either through normal biological processes (being used up by the inhabitants) or by being removed by the protein skimmer. ECO STRONTIUM has been specially formulated to replenish strontium and provide a rapid, bio-available strontium source for corals and other marine organisms that produce calcareous skeletons. Potassium has also been added, as it will benefit the symbiotic algae growing in coral and other invertebrate tissues. With regular use of ECO STRONTIUM, corals will grow more rapidly and remain open for longer periods. Contains no gluconates, EDTA or other organics that cause dissolved organic carbon levels to rise. For best results, use ECO KALKWASSWER or ECO CALCIUM PLUS first. 8 oz. bottle treats up to 4700 U.S. gallons (17,791 liters).Phosphate & nitrate free!