Seachem PhosNet is a granular ferric oxide (GFO) with high porosity, high surface area and high binding capacity. It will rapidly remove phosphates and silicates from both freshwater and saltwater and will not release them back into your aquarium. It exhibits stronger binding than most competing products and consequently can reduce phosphates and silicates to very low levels. PhosNet™ also offers less dust and thus is easier to use than most competing GFO products. Use 50 grams for every 50 gallons saltwater or 100 US gallons freshwater. Leave product in place for 4 days, then test phosphate or silicate concentrations with either the Seachem MultiTest Phosphate Test Kit or the Seachem MultiTest Silicate Test Kit It may be used in a canister filter, media chamber, box filter, or any high flow area of a trickle filter.