The Dymax Slim Flo replacement filter cartridges work to keep the aquarium water clean and clear. Combines mechanical and chemical filtration. Each cartridge is able to filter and trap particles and waste as well as to remove odour and colouration so as to provide good water quality and clarity. Dymax Slim Flow Cartridge SFC-ML suits the Slim Flo SF-240 and SF-500 and contains wool and carbon. Each cartridge is recommended to be used for not more than 60days. DM574