I was having similar problems when it started warming up a couple of months ago and used the computer fan method that Seahorsedreams linked to. Worked great and cost me less than $20 for two fans and the power supply. Beats the heck out of an expensive chiller.
I've thought for years about a
DIY chiller that was made from one of those little fridges people use in offices and dorm rooms. I'd cut two holes in the front door for the in and out tubes. Inside the fridge, I'd have some pitchers of water (or something similar) with tubing wrapped around them as many times as possible. You could use some sort of temp controller to kick on the pump that pushes water through the system. One of these days, I'll give it a try -- probably when I have a tank large enough to warrant it.
