you can make a handy dandy chiller yourself with a foam cooler, a long coil of tubing, and a bunch of freezer packs.
just run a line from your tank or sump to a large pump. the outlet goes into the cooler where it spools around the freezer packs affectively lowering the tempture before it heads back to the tank. simply rotate out the freezer packs with fresh ones daily.
It takes some fine tuning to get it balanced right, and it does require daily attention, but It will help get you through those hot summer months.
Inccidently, I was able to lower my tanks temp. a full 2 degrees simply by lowering the room temprature a bit.