I'd always made provision for this mod, which I've now actually completed. Here is what the extra (non-fan) hole I made in the backplate was for.
I ripped the male power connector out of a dead/dying PSU and modified my eheim 1250 to use it instead of standard plug. This way I just plug a standard power cable into the plug and my pump is active. This was really easy, just my soldering iron and wire clippers.
I took so long to do it because I was originally going to use a 120V relay (normally open) to open or close the green wire on the ATX power connector. With the pump not plugged in, the green wire would have been an 'open' and the machine would not have been able to power up. Keeps you from powering up w\ out coolant flow. I couldn't find any 120V relays (well, 120V coil relays) locally so I've postponed it for now. I may or may not revisit it... Ideally I'd like to get a flow switch but they're shockingly expensive!
Okay, pics.
