This is a super bio-ball with sponge inside. It can not only provides the maximum surface area for nitrifying bacteria growing, but also promotes gas exchange and upgrade oxygen level. Perfect filtationaquarium filter bio ball that helps clean your water naturally, beneficial to oxidation of oxygen convection exchange, and for reproductive growth of nitrifying bacteria with a huge biochemical surface area. Max surface areabio-sponge inside provides more surface area for growth of beneficial bio-spiral bacteria. Many flake structure, internal porous, great for any freshwater or saltwater. Better effectthe bio ball is idea for external and pressurized filters in aquarium tank, pond filter and fish farm water treatment. Safe filter mediagood to use in different type of filters, encourages growth of biological colonies, more capacity than most biological filter media, reduces and controls harmful ammonia and nitrate. Perfect shape56mm in diameter. Packaged in mesh filter bags allowing easy cleaning, promote gas exchange and increase dissolved oxygen levels.