The Fluval U3 Underwater Filter is ideal for use in fresh, marine or reptile environments. It comes complete with the Adjustable 3-Way Flow Control feature, 2 Foam Pads, 2 Poly/Carbon Cartridges, and BIOMAX Biological Rings The U3 is suitable for aquariums from 90 to 150 L (24 to 40 U.S. gal.). Other sizes available: -A465 Fluval U1 Underwater Filter, for aquariums up 55 L (15 U.S. gal.) -A470 Fluval U2 Underwater Filter, for aquariums from 45 to 110 L (12 to 30 U.S. gal.) -A480 Fluval U4 Underwater Filter, for aquariums from 130 to 240 L (34 to 65 U.S. gal.)