Suitable for aquariums up to 25 gallons, the AQUATOP PF25-UV Power Filter includes U.V. Sterilization, a self-adjusting surface skimmer and replaceable filtration media. The PF25-UV is capable of filtering up to 90 gallons per hour and includes an adjustable flow rate. This convenient Hang On Back style filter has a built-in, self adjusting surface skimmer for cleaning the surface of the water and to promote gas exchange. The featured UV Sterilizer of the PF25-UV requires no extra plumbing, allowing for a quick and easy installation. The UV Sterilizer of the PF25-UV helps eliminate unwanted algae blooms, keeping aquarium water crystal clear and aids in the health of your aquatic creatures by eradicating free-floating parasites. The PF-UV Series fits on aquarium rims up to 3/4", and comes equipped for mechanical, chemical and biological filtration. With a replaceable filter pad enhanced with AQUATOP's Bamboo Carbon, ceramic rings, UV Sterilization and a self-adjusting surface skimmer, the PF25-UV is a unique filter for all your aquarium needs.