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 mediaRemoves ammonia, nitrite and nitrate from fresh, salt and reef tanks1 liter is equivalent to over 40 L of typical plastic ball mediaEach liter of Matrix provides over 160,000 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.