Trace elements are important in maintaining the overall health and vitality of the inhabitants of a reef aquarium. Although typically contained in most salt mixes, these elements are rapidly depleted in a normal reef system, either through normal biological processes (being used up by the inhabitants) or by being removed through protein skimming. ECO NF Metal has been specially formulated to replenish these trace elements to ensure the continued rapid growth and well-being of the organisms in a reef aquarium. The special blend of trace elements helps bring out the natural blue, red, and yellow in your corals. The ECO NF Metal additive is designed to be immediately bio-available to all the animals in the aquarium for fast results. Phosphate and nitrate free! 8 oz. bottle treats 5000 U.S. gallons.