I needed (wanted) a 3 degree temp reduction in my tank and used a small cheapie refrigerator to accomplish the mission. I bought a small one from Home Depot for 50 bucks and 250 ft of 1/2" hard poly tubing with appropriate fittings. I use a Maxi-Jet 400 (106 gph) power head to push water through the unit and got a 5 degree cooling for my system, a 46 Bowfront with a 30 gal sump. I drilled the back of the refer and brought the supply and return in and using 3 tees and one coupling split the 'cooling coils' into 4 50' coils then back into a common return using another 3 tees and a coupling. This slowed the flow trhough the coils to aid in thermal transfer. I cut a 5 gallon plastic oasis water jug to fit into the refer and put the coils inside it. I keep the jug filled with fresh water to add some thermal mass and cranked the refer to max cool. When the water in the jug was cold, I started the saltwater flow through the unit. At 24 hrs, my system was at 79 down from 82, at 48 hrs the temp settled at 77 and has stayed there ever since. The refer runs about 40% of the time and the whole system cost $94 not including the power head. Beats the heck out of a $600 chiller. I have since covered the water in the 5 gallon jug with spray foam to keep from having to defrost the refer and haven't added water to the thing in 6 months.
