The Boyu undergravel filter is designed to fit tanks with approximate dimensions of 23\"x- 12\" . Due to the 16 piece plate system, you can use this kit with smaller tanks (having spare plates for future use) or even add a further kit for larger aquariums. It is also suitable for use in almost any shaped tank, due to the versitility of the plates. Features The undergravel filter is a biological aquarium filter and makes your gravelact as your filtration medium. 16 x undergravel filter plates - 5.5 inch x 2.75 inch. 1 x uplift tubes. 1 x air tubes and 1 x small air stones How does an undergravel filtration system work? The plates assembled together sit under the gravel. The uplift tubes connectto the plates and rise up to the water surface. The system is then run using either a traditional air pump or power-head waterpump. (not included) The entire gravel bed becomes a filter medium for hosting the bacteria neededto breakdown fish waste making it act as a biological filter. Depending on the type of fish you are keeping, uplift tubes can be fitted with simpleair stones that provide slower water current, or power-head water pumps thatprovide a strong current.