Seachem - PhosNet 125g
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.