UNIVERSAL DESIGN: Tetra Whisper 10-30 Internal Filter is an all-in-one air pump and water filter system. USE IN: Aquariums 10-30 gallons in size. INTERNAL FILTER: Mounts on the inside of your aquarium with clip (included). CATCHES DEBRIS: Dense, dual-sided mesh filters debris and fish waste. AERATES WATER: Air-driven design filters water while oxygenating water. CONVENIENT DESIGN: Uses easy to change Bio-Bag cartridges; filter mounts inside aquarium, making it possible to place tank flush against the wall.