Julien Sprung's Phosban is a highly effective way to control phosphate levels in aquariums for months at a time. Can be used in both saltwater and freshwater aquariums. Highly porous ferric oxide hydroxide granules absorb phosphates, silicates and dissolved organics without any risk of these substances being leached backed into the aquarium. Use just like carbon. Filter bag included. Treats 150 gallons.