I have a 110gal tank with 6 goldies in it. It has 2 aquaclear 110's on it. I clean it out weekly. About three weeks ago i was cleaning it out and removed all the media so i could get down to clean the impellers. I then put it all back together and started it up when the tank was finished filling. When it started up it was making a quiet grumbling sound but it wasn't really all that noticeable. I just finished cleaning it out today and when I put it all back together and started it up again it's pretty loud this time. It doesn't sound like it's rattling apart or anything but it doesn't really sound normal. Has anybody had a problem before with noisy 110's?

I have never had the problem with my 110 but have a couple of ideas. Perhaps one of the impeller blades were bent when it was being cleaned? Or maybe a small piece of hard debris in the impeller cavity?

I had that happen, well, at least something that sounds like it. What it was for me, was that the impeller wasn't properly seated. It took two tries to get it back in right, but once I did, it was quiet as can be. Just a thought....

Of course, I dont know why I didn't think of that too. That has been an issue before on my marineland filters.

I would definitely look to a mechanical issue, since you said that the noise had not started until AFTER you cleaned the impellers. I would triple-check to make sure that, like Lynda said, the impellers are properly seated and, like br553 suggested, there is not anything that inadvertently fell in.

ACs in my experience are quiet, reliable filters.