Corals require iodine as a de-toxifier, as a protection against uv radiation and as a natural defense against many parasites. Iodine is present in natural sea water in a very low concentration (0.06 mg/l). Iodine occurs in natural sea water in different compounds. These include iodide, iodate, molecular iodine and hypoiodite. Generally when we say iodine we mean one or more iodine compounds without clear distinction. Natural sea water contains predominantly iodate and to a lesser extent iodide. Salifert's Natural Iodine supplement contains a large portion of iodate and also some iodide in similar proportions to natural sea water. Both are present as their calcium and magnesium salts, this has been done because Salifert's research has shown that iodate is complexed with calcium and magnesium in natural sea water. Another advantage of using these salts is that no ionic imbalance is created unlike when potassium or sodium salts are used. Salifert stands alone in offering such an advanced well thought out formulation. Directions: Shake well before use. Dose 5ml per 100lts once every 2 to 3 weeks. Every 5ml per 100lts will increase the iodine concentration by approximately 0.04mg/l. Maintain an iodine concentration of 0.03 to 0.10mg/l.