This test can only be used for marine water Iodine is present in NSW (Natural seawater) in a very low concentration (0.06 mg/L or 0.06 ppm). Iodine occurs as different species. Some of them are iodide, iodate and hypoiodite. Generally when we say iodine then we mean one or more iodine species without a clear distinction being made. NSW contains predominantly iodate and to a slight extent iodide.There is however a misconception among many hobbyists that iodide predominates in NSW. This is however false. Test kits which are not capable in detecting iodate might not really be suitable for aquarium use. Since in an aquarium iodide can be transferred to iodate. This means that if a test kit is used not capable in detecting iodate, a false low total iodine concentration (sum of iodate and iodide) will be obtained and the iodate concentration can climb far too high and possibly upsetting the aquarium environment. The Salifert Iodine Profi Test measures all naturally occurring iodine species such as iodate, iodide, molecular iodine and hypoiodite. No other test kit offers this possibility. Saliferts Natural-Iodine additive is highly concentrated and contains a large portion iodate and also some iodide. Salifert stands alone in offering such an advanced and well thought formulation. Approx. a total of 40 tests per kit. Measures iodide and iodate (together with hypoiodite and molecular iodine) in separate steps.