Only thing I can see being a fault of them is that they sit on the outside of the glass. I just think that if you don't have your tank as an in wall tank it will look wierd having something like that sticking out on the side of the aquarium with power cord. Now if they made some kind of deflector to direct flow right and left so that you could put it on the back wall would be good. said:You're right, but IMO big pumps in the tank look wierd too! :lol: