In almost any aquarium a film of including micro organisms dust oils and food fats form over time. With the ehim skim 350 surface skimmer you can efficiently eliminate this film and have glass clear water surface and high oxygenation. The eheim skim 350 although designed for constant use is also suitable for short term use. If using alternateley in several aquariums please make sure that algae spores or diseases are not transmitted from one to the other. Wattage 5w adjustable flow self leveling extractor for when the level rises and falls. Suitable for both fresh and saltwater. 40.5mm w x 132mm h x 54mm d.