Fluval Nano Carbon Cartridge fits the Fluval Nano Filter and contains highly porous carbon that effectively adsorbs odours, discolourations, and impurities. Large amounts of surface area in the carbon effectively remove heavy metals, organic contaminants, and pollutants, leaving aquarium water crystal clear and sparkling. The custom-designed cartridge easily slots into the Nano Filter’s filtration chamber. The package contains 2 cartridges.