The EHEIM Coarse/Fine Filter Pad for the Professionel 5e 450/700/600T is a premium dual-layer foam cartridge designed to provide both mechanical and biological filtration for large external canister systems. The coarse blue foam layer traps larger debris and the white fine foam catches smaller particles, while both support beneficial bacteria growth for nitrogen cycle stability. The pads are washable and reusable—simply rinse and gently squeeze them to preserve the bacterial colony and maintain excellent water clarity in freshwater or marine aquariums.