Reef Iodide is a concentrated source (8.000 mg / L) stabilized potassium iodide to reef aquariums that will reply and maintain iodine levels found in natural sea water. It is formulated to provide a safe source of iodide that will not become toxic free iodine during storage or under the conditions of the reef aquarium. Iodine is as toxic as chlorine and should never be used in a reef system. However, the iodide is as safe as chloride.