Precision Iodine is a highly concentrated, Iodine supplement that is ideal for Marine Fish and Reef aquariums. Proper Iodine levels will help corals maintain their natural color, protect them against bleaching and help them open more fully. Iodine also assists crustaceans in performing the process of molting. In addition, Iodine has important properties for fish. It will aid the metabolism of fish by providing Iodine for the thyroid gland, which helps maintain strong coloration and a vigorous appetite.