Algarde Undergravel Filter Algarde Undergravel Filter – The Under Gravel Filter is a perforated plate to be placed on the bottom of the aquarium under the gravel. Water is pulled through the gravel, under the plate, and up through lift tubes. Provides superior biological filtration. It comes with a clear plastic uplift tube, top and bottom fittings, a plastic plug and approx 1m of airline tubing. The uplift tube can be fitted at either end and removed for easy cleaning without disturbing the base plate It is suitable for use with and air pump or power-head pump (Both not Included) The Under Gravel Filter Plate can be cut to fit a smaller tank or used in conjunction with other plates for a larger tank.