I had the same prob. I took a Soda cooler, drilled holes oppisite each other on the sides of the cooler, about 4" from the bottom. Attached a quick connect to the hose of my return on my canisterand connected longerhose which runs thru the cooler in a coil. Then out of the cooler and another quick connect back to the tank. I fill the cooler with alittle water, then keep frozen pop bottles in the freezer. I put three at a time in and keep the lid closed. Stays cold almost 2-1/2 days, then replace the pop bottles. Not the prettiest but my tank stays cool now. If you dont have a canister type filter, im sure there is a submersable type pump you can use in the cooler to recirculate the water and just make it loop in the tank. I hope this made sense, it has really worked great for me

Oh I also put pipe insulation all the way up to the tank on the outside of the cooler were the chilled water comes out of the cooler. This keeps the water cold until it reaches the tank.Hope this helps someone :?