Help your finned friends breathe easily with the Penn-Plax Cascade 100 Power Hang-On Filter. This filter features a Bio-Falls Quad Filtration System to keep your tank fresh and clean! The polyfiber floss cartridge traps floating particulate matter‚Äîwhile the activated carbon cartridge removes harmful chemicals， toxins， odors， discoloration， and other contaminants from the water. The internal sponge optimizes the colonization of beneficial anaerobic bacteria while removing ammonia and nitrites. The external Bio-Falls wet/dry biological booster provides anaerobic bacteria for additional ammonia and nitrite removal， while enhancing oxygen exchange for maximum water oxygenation. It features an adjustable flow knob that allows you to reduce filtration during feeding times， or as needed. A leveling device keeps your filter in position， and the self-priming intake tube has a built-in， extendable stem to allow placement of the intake strainer close to the bottom of most aquariums. It is suitable for fish tanks up to 20 gallons in size.