The Elite Double Sponge Filter is an air driven filter that efficiently oxygenates and filters aquarium water. Both biological and mechanical filtration are accomplished by two foam filters that trap floating debris and biologically cleanse aquarium water. To maintain effective biological filtration it is recommended to rinse the foam filters in water taken from the aquarium and to alternately replace them when necessary. Oxygenation of aquarium water is best achieved by locating the vertically adjustable outlet at the water's surface. The Elite Double Sponge Filter is a compact internal filter system that can be conveniently positioned in a variety of locations within the aquarium and is completely safe for even the smallest baby fish