Biocell biological filter media is made of neutrally buoyant, "high-impact" polystyrene that provides a surface area of 198 ft²/ft³ for nitrifying beneficial bacteria. Biocell media's size and surface configuration provides highly protected surface-areas (protecting colonies of nitrifying bacteria) while offering the added benefit of self-cleaning. Bio cell's neutral buoyancy combined with routine backwashing prevents clogging, while maintaining an excellent environment for nitrifying aerobic bacteria.