The Fluval U1 is a compact and versatile internal filter for aquariums up to 55 l. This small aquarium filter is very comfortable in handling. The outflow can be regulated and it can be mounted vertically or horizontally in the aquarium. Thanks to the flexibility in the positioning of the filter, it can be used as a primary filter in smaller aquariums or as a supplementary filter for larger aquariums. Their unique ability to be placed at the bottom of your aquarium makes it ideal for low water levels. The removable central core allows use of chemical or biological media.Fluval Aquarium Internal Filter U1+ new sleek design+ new easy grip water control paddle+ new redesigned media cartridge - Traps more debris+ the filter cartridge can be used for inserting the Fluval Clean & Clear media+ designed for aquariums up to 55 L+ use as a primary filter for smaller aquariums, or supplementary filter for larger aquariums+ position horizontally for shallow tanks, larger tanks with low water level