Used Coralife skimmer for sale. Can be used as a HOB or in sump but works best in sump with a stable water level. Skimmed some nice nasty green stuff out of my 75 gallon reef tank. The only problem is that the clip holding the air silencer on is broken so I just used an elastic band to hold it on. Doesn't affect the function at all. It could probably use a bit of a vinegar soak to clean it. At $30 it's a bargain.