Cascade Power FiltersThe Penn Plax Cascade Power Filter contains a polyfiber floss cartridge that traps floating particulate matter. Activated carbon cartridge removes harmful chemicals, toxins, odors, discoloration and other contaminants. Extendable self priming intake tube to get strainer near the bottom of most aquariums Adjustable flow control knob for reducing filtration during feeding times Internal shelf system spaces carbon throughout cartridge Internal sponge