Nourish is a comprehensive vitamin, amino acid, and trace element supplement developed to address nutritional requirements commonly associated with long term closed system housing of freshwater ornamental fish. Nourish contains potassium iodide in a heavy base of spirulina and chlorella. The nutrient iodine is essential for the biosynthesis of the thyroid hormones thyroxine and triiodothyronine.* Both spirulina and chlorella contain a rich assortment of amino acids and vitamins. Nourish can be used on marine ornamental fish; however, it is specifically designed for freshwater fish. *Nutritional Requirements of Fish, The National Research Council of the National Academy of Sciences, National Academy Press, Washington, DC, 1993, p. 21.