Hmm found 50' length of titanium .5" OD tubing for $50 on ebay, and large fridge compressor, 120v-1/4hp new in box for $25. I suppose could actually mount the condensor and fan outside, like a home a/c unit, and mount the compressor and evaporator/heat exchanger under the tank. Would make for a definate permanent installation but should actually work pretty good. with a temp controler that basically kicks a relay to run the circulating pump. For a permanent type installation a small length of schedule 80 6" SS pipe with water/glycol mix, copper evaporator coil wrapped inside, titanium tubing inside, filled with water/glycol mix. The compressor would cool the fluid which would cool the aquarium water running through the tubing. Figure $150 for the pipe, tubing, and compressor and then use the condensor I have that came from old ford torino. I can sweat all the copper tubing connections for the compressor and actually have a vacuum pump and gauges to fill the compressor with R134A freon. 1/4hp chiller for under $200 and designed to fit in my stand dosent sound like a bad deal!