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. SMALL - Each Bio-Pin Ball has 110 Bio-Pins (drip points). There are 120 balls per gallon. One Cubic Foot of media has approximately 130 Square Feet of surface area