Help: Using power supply to run fans away from case

Hey guys,

I need to use some computer fans in my other expensive hobby, aquariums. I have a 75 saltwater reef aquarium with around 500 watts of light in the hood. This puts out a lot of heat which causes the water temp to rise to around 84 degrees which is a little too high for a reef tank. I've read that installing a couple of fans in the hood can lower the temp by a few degrees and the ones they sell at the petstores are around $40 each. They look just like a computer fan except you can plug them into an electrical outlet.

Here's my question. I have an extra power supply and several extra computer fans and I would like to set them up in the hood. How do I set the power supply up to turn on when I plug it into the wall. Is this possible without a motherboard?

Thanks,
Doug