The EZ-Clean Dual Cartridge Internal filter offers a unique alternative to traditional internal filters. Its large, cartridge based filter system offers mechanical, biological and chemical filtration for small aquariums. The filter offers aeration of the return water flow and an easy to use water change feature. designed to fit unobtrusively in the coner of an aquarium, it features a filter cartridge that's quick and easy to change. The filter also offers a unique water changing feature that makes siphoning water from and adding water to the aquarium both quick and easy.