This is the most important component of RAS because it helps in removing the fine pollutants from water during waste treatment. The media within the filter is made up of materials like plastic sheets, beads, lava rock, gravel or sand grains. The properties of the media should be such that it should have a high surface area for bacterial growth, pores of movement of water, clog resistant and should be easy to clean.
A simple biofilter can be a wheel, barrel or box filled with media on which nitrifying bacteria grow. It can be made of plastic, wood, glass, metal or concrete. The size of the biofilter defines the fish carrying capacity of the entire system. The surface area of the filter should be large so as to accommodate high- density bacteria to process loads of waste present in the fish tank. While designing biofilters the surface areas, ammonia loading and hydraulic loading should be properly estimated.
