Features: 3 in 1 design, it can be used as a filter, a oxygenation pump and can be used for water circulation. High efficient and energy-saving, perfect to help improve water quality so as to keep your aquarium in optimum condition. Waterfall water flowing design, ultra quiet working. For the first time use, you need add full of water then it can work. For type 2/3/4/5/6, it is with oil removing membrane processor, which can adsorb redundant oil from the surface of water. Adjustable distance between the filter and the fish tank, and adjustable water flowing through the adjustment controller. Once power-off, you can restart it without adding water again. Easy to install, also easy to maintain. There are different types available for your choice.