Aqua-Tech makes aquarium maintenance simple and easy. The Aqua-Tech Power Filter for aquariums traps dirt, removes impurities and offers maximum water to carbon contact with its advanced three step filtration. This product comes in a variety of sizes to meet any aquarium needs including: 5 to 15 gallons, 10 to 20 gallons, 20 to 40 gallons and 30 to 60 gallons. Complete 3 Stage Filtration System: In Stage 1: • The filter cartridge floss screens out dirt and debris. • Molded and ribbed back for maximum water-to-carbon contact. In Stage 2: • Activated carbon inside filter cartridge removes odors, discolorations and impurities. • Change the used Aqua-Tech replacement cartridge monthly as carbon deactivates with use. In Stage 3: • The Bio-Tech Biological Grid*, which comes with your power filter, never needs replacing; ensures elimination of toxic ammonia and nitrite; and has a unique design that will not clog!