If you find the mp40s grindy sounding, that's only cause they aren't correctly aligned with wet side and dry side. When properly aligned, they just sound like a turbo from a car. Turn them down to about 75%, and the sound is negligible.

I know what you mean about mis-alignment, but I did play with them

I could not make them any quieter, regardless of how much I moved them around ...

It wasn't vibration, it was just the dry-side bearing noise

I haven't heard any MP10s, so you're very right that my conclusions could be different as a result.

And, I have two very noisy pumps in my return, as well as a noisy overflow. I may have just become accustomed to a really noisy tank (and it is in our bedroom, of all places).

I'm sorry to hear you have noisy returns

We sleep next to our tank, too, but luckily I was able to punch a hole in the wall and set up the sump in my office
We still hear the hum of 2 pumps ( which drives me nuts ), although the wife says it's all good

I wish I could hear your tank :wink:

My return pump is great (Eheim Compact 2000). Super quiet. It is the Maxi Jets that are connected to the fluid reactors and the chiller that I would like to smash with a hammer. I'm picking up a Compact 3000 as soon as I stop screwing around on the forum and get my backside out the door, and the MJs will be coming out. Then I'll get to listen to the slurping and splashing in my overflow again. I digress.

This thread has been hugely informative for me. While still a couple of months off, I was debating going larger than the MP10s for the 40B.

We also wanted to smash our 1/4HP chiller it's first few days next to the tank
This was summer of 2010 on our 125g FW - there was quite the heat wave here then
After some thinking decided to plumb it around the wall to my office and was quite shocked when the wife said, 'save all that lost plumbing and punch a hole through the wall'

Went from 12+ feet of head to about 5
Gotta love my wife lots :mrgreen:

I had 3 mp10s on my 90 and at full speed they would whine but at anything less than 90% it was silent. I think an mp40 on a 90 would be crazy flow. I have 2 on my 225 and they are turned down so I can keep my sand in one place lol. They arw at about 60% and are very quiet.

Id stick with 10's if I was you Greg. I really wanted to run 6 mp10's but the glass was to thick so no go.

I was thinking about the mp60. Does any one know what there noise level is compared to the 40?

Did you mean your Eheim pumps ? I have 2 of them in my tank too, they are dead quiet because I have connected them with vinyl hoses instead of pvc pipes. Even so, when I touch the hoses, I still can feel the strong vibration from them or when I just touch the outside sump, but no noise at all. You can use just a few inches of vinyl hose first then attach it with the pvc pipe, it can help to reduce the humming sounds too.

Foam pipe insulation also absorbs some ofthe vibration