Tropic Marin Pro-Coral Mineral are crystallized trace elements to stimulate growth and health of all invertebrates. In saltwater aquariums with a high invertebrate population, a lack of trace elements can lead to impaired growth and invertebrate deformities. Pro-Coral Mineral contains a concentrated form of all trace elements, including iodine and strontium, that are found in natural sea water. Without chelates, phosphates and nitrates.Tropic Marin Pro-Coral Mineral+ crystallized trace elements for the health and growth of all invertebrates+ contains a concentrated supply of all trace elements found in natural seawater+ for color intensity, health and growth of invertebrates+ includes iodine and strontium+ does not contain chelates, phosphates or nitratesApplication Tropic Marin Pro-Coral Mineral:Add 5 g (approx. 1 level measuring spoon) each week per 50 liters/13 US Gal. of aquarium water. This increases the proportion of strontium to approx. 1.5 mg per liter and iodine to approx. 0.0