With the Salifert Profi Test Si you can determine the Silicate content in freshwater or seawater exactly and easily. Silicate occurs especially in tap water or in purified water when the RO or DI unit is not functioning properly. Silicate not only results in diatom bloom but might also block some essential trace elements such as vanadium and molybdenum. For freshwater, please do not use tap water or Osmosis water with more than 2 mg/l silicate content. In seawater the silicate content should not be determined with these test kits. The Salifert Profi Test Si -Silicate- is for approx. 60 tests in seawater or freshwater. The range is 0.03 - 30 ppm as SiO2.