In the meantime, you can fill a couple of empty softdrink bottle with water, freeze them down and float them one at a time in the tank to bring the temp down. If you use 1 at a time, you always have 1 ready to go in the freezer if needed. It's what I did last year to try and bring the temp of my sorority tank down. Got up to 36 deg before I noticed... Worked a treat. I have a friend who has converted an old bath tub into a goldfish pond. She does this every year to stop her fish boiling in the summer heat...