Multi-stage filtration that includes biological, chemical and mechanical Easy access for quick routine maintenance with included hang on the back polishing unit Multiple water return options for optimal versatility to best suite a variety of aquarium habitats; spray bar, water director and water polishing unit Water Polishing Unit uses Large Aqueon Replacement Filter Cartridges; replace monthly Internal media replacement; carbon change every 30 days, foam pad rinse or replace as needed, white polishing pad change as needed Includes quick disconnect valves, pump locking heads, water intake/output connections, hoses, water polishing unit with cartridge and media: activated carbon, coarse foam, bio-balls, bio-ceramic rings Fits aquarium size up to 55 Gallons.