I've got one. I originally bought it for a FW tank. After switching over to SW, I used it for a bit. Now I use it to mix my saltwater. I think about putting it back into my tank every now and then as an extra PH, but I haven't yet (been two years now).
It's a perfectly fine pump. I've never had any trouble with it really. But here are my issues (why it's now my mixing pump):
1. Not enough flow -- if I'm going to put in a PH, I want more than 170 gph out of it, especially for a 30g to 40g tank.
2. Uses suction cups to hold onto the glass. The round pump body fits into a holder which is then suction cupped to the glass. I don't like suction cups. That being said, I never, ever, in two years had my eheim suction cups fail on me. But who's to say ...
Anyways, it's an Eheim pump so it'll be good quality. It's a little difficult to remove the impeller cover it's been a while since I last cleaned it. But the pump's solid.
Hope this helps.