Fluval U2 Underwater Filter provides complete and efficient 3-stage filtration, including BioMax biological filtering, to create superior aquarium water quality. The U2 Filter includes practical and versatile features, making it ideal for application in fresh, marine and reptile environments. The filter provides the option of setting the flow output in 3 different positions, a key benchmark in underwater filtration. The adjustable 3-way flow control feature lets you position the water flow output to meet your specific needs. The Top Output setting provides maximum circulation and oxygenation, the Integrated Spray Bar setting provides a gentle, even flow for planted aquariums, and the Bottom Output setting is for deepwater agitation. The filter also has a convenient flip-top lid that allows quick and easy access to the filter cartridge for maintenance or replacement. The filter can be installed vertically against the aquarium wall to create currents or customized flow patterns; it can be placed horizontally in shallow water tanks; or it can be used to create decorative features such as waterfalls. The U2 Filter comes complete with 2 Foam Pads, 2 Poly/Carbon Cartridges, and BioMax Biological Rings. The filter is suitable for aquariums from 45 to 110 L (12 to 30 US gal).