duster

I ran a mag 18 internally for two years, then externally for two and have recently put it back into the sump as a return. My temperature has ran hotter on the tank since resubmerging it. I now run an external Gen-X PCX 40 (comparable to iwaki MD50RLT) and can tell you from experience, its louder than an iwaki. To avoid confusion, I have two return pumps.

If your trying to find a real quiet return pump. Id suggest an eheim 1262 (900GPH) sumbersible. It won't create nearly as much heat as most other submersible return pumps.
Or, if money is no issue, a Red dragon submersible return pump.
Melev just did a product review on the new Maxijet utility pumps. Maybe one of those would work for you.

I used a blueline that was totally silent! Presently, I'm using a Mag and the newer MaxiJet 5500 without complaints of noise or heat.

Is your Iwaki US made or Japanese made? I have seen a video on youtube and it showed the difference between the Japanese made Iwakis and the US made ones. The Japanese made ones are much quieter than the US made ones.

I have never had a sump before. When I set one up I'm using an external pump to cut down on heat issues. I live in San Diego so heat is definitely an issue with my system. If someone lived in say Michigan I'd suggest them to use a submersible pump to help heat the tank during the cold times of the year.

It is the Japanese model, and has a very distinctive hum. I live in Texas, so the heat is also a factor. I am kinda of used to the hum of the Iwaki, but have visited tanks that ran very silent. if i could eliminate that my wife my would be extremely grateful.

Why not use the new Maxijet Utility pump then? It can be run externally too.
http://www.reefaddicts.com/content.p...m-Utility-Pump