Seachem Matrix Bio Media is a highly porous media designed to provide exceptionally efficient biofiltration for single site removal of ammonia nitrite and nitrate from freshwater marine and reef aquaria. Premium natural bio filter support media Removes ammonia nitrite and nitrate from fresh salt and reef tanks 1 liter is equivalent to over 40 L of typical plastic ball media Each liter of Matrix provides over 160000 cm2 170 sq. ft. of surface equivalent to over 40 L 10 gallons of typical plastic ball media This product is sold by volume. Cited weight is minimal weight. Directions Use 500 mL of Matrix for each 200 L 50 gallons of water. Matrix may be placed in any kind of filter and is particularly effective in a canister filter. Matrix is sufficiently large that no filter bag should be required for most applications. Matrix works well in drip tray systems but you may find that the larger Pond Matrix is better suited for such applications.