State of the art filter media for use in fresh and salt water wet/dry systems. They may be connected together or randomly placed in the filter box. Bio-Pin Balls help produce turbulence, aiding in the gas-exchange process. The void space between the Bio-Pins is ideal for the movement of gasses like oxygen and allows it to more-readily come in contact with nitrifying bacteria living on the media surface. Biological filtration is the process by which waste is broken down from toxic ammonia to less toxic nitrates. The suggested usage is 1 gallon of Bio-Pin Balls per 20 gallons for salt water or 35 gallons freshwater. •LARGE - Each Bio-Pin Ball has 150 Bio-Pins (drip points). There are 74 balls per gallon. One Cu. Ft. of media has approximately 150 Sq. Ft. of surface area.