Synthetic ferric oxide hydroxide granules with an extremely high capacity for adsorbing phosphate from saltwater and freshwater. Also adsorbs silicate, and does not release absorbed substances. Recommended by Julian Sprung for long-lasting and easy control of phosphate levels on a permanent basis. Media bag included.Specifications* 150 grams will treat up to a 150 gallon tank for several months (depending on the phosphate level). Replace when phosphate levels start to rise.* Media bag included.