Fluval U1 Underwater Filter provides efficient filtration to create superior aquarium water quality. The U1 Filter includes practical and versatile features, making it ideal for application in fresh, marine and reptile environments. It has a convenient flip-top lid that allows quick and easy access to the filter cartridge for maintenance or replacement. In addition, the filter can be installed vertically against the aquarium wall to create currents or customized flow patterns; or it can be placed horizontally in shallow water tanks; or it can be used to create decorative features such as waterfalls. The U1 Filter can be used as a primary filter in smaller aquariums or as a supplementary filter for larger aquariums. It is also ideal for tanks with low water levels. It includes an adjustable flow control and comes complete with 1 foam pad. It is suitable for aquariums up to 55 L (15 US gal).