I'm using a Mag 7 to circulate the water from the tank to the sump and it's sitting in the sump. When I first put it into the sump, there was some vibration, but I just moved it around and found a "sweet spot" and it's totally silent now. I also have a Mag 5 in there that drives my UV
, which is also totally silent.
If you just put it into the sump and haven't tried shifting it around, do that before you take any other measures. If it doesn't work, foam like they use in an Aquaclear filter most likely will stop the vibration. I got the Mag because I started with a Rio HF and the only way to stop that from making a really nasty noise was to just get rid of it.