In addition, if the Mag3 ever needs servicing you can replace the impeller assy as a unit for 9 dollars. I have two extras on hand if I ever need them.
Krazy you said it has no magnets, I guess you meant to say it has no BRUSHES. It does have a magnet in it.
There is no shielding around it though, something to be aware of if the pump will be close to a CRT type monitor. It will cause the screen to flicker. Since my PC is on the floor about 3 feet from the screen, its not a problem for me. As far as interfering with the PC itself or disks, I tried leaning a floppy against the pump and cycling it on/off several times, and it lost no files.
I didnt bother with a relay or anything for it, I just plugged it in. Just guessing, it ought to run continually problem free for a few years at least.
Here's a good supplier for this pump...
http://www.reefgeek.com/