EHEIM - Coarse Filter Pad for 2217 Canister Filter - 2 PadsDESCRIPTION EHEIM's Coarse Blue Filter Pad is used as a parting layer between the mechanical and biological filter medium. Coarser particles are restrained and are thus removed from the water prior to entry into the biologically acting filter layers. This filter material may be rinsed and re used; rinse with tank water or dechlorinated tap water to keep it's biological filtering capabilities. Incoming water is treated and pre cleaned before it flows