i have two ehiem pro 2 and a ehiem pro 2 knock off all sitting aprox 3 feet higher then my tank. The only problem is when the power goes out or i clean the filters. I have to use a powerhead to reprime them. Aint hard at all . Did have a xp3 didnt like it. i also had a ehiem classic and a ehiem eco up there at one time and they worked fine if i primed them