Emperor 400-noise reduction?

[justlooking]

Have my emperor up and running for like a year and now its making some type of grinding noise. The noise disappears if I lift the filter cartridge or filter media container up above where it should be. What could be the source of this noise. Its annoying. Only other problem with the filter is the algae build up on the filter, but once every other day I take the filter piece off and clean it.

 

[gregzbobo]

Impeller is a bit out of alignment, mine on my 55 freshwater tank does this every time I take the impeller houseing out to clean it. Takes a bunch of fiddling to get it silent again, but it always gets silent. Just fiddle with it, lift the impeller housing up a hair, shove it back in hard, move it back a hair, to the front a hair, find the spot where it shuts up. Hope that helps.