11.1.6 MAKING AN INEXPENSIVE COOLER:
Rather inexpensive coolers can be made using a small second hand freezer. Many hobbyists have tried it and they work fairly well. One can reduce the temperature about 4-5 degrees if the system is properly set up, and if metal type tubing is used to conduct the water in and out of the freezer.
You must run water very slowly through a small diameter tube that enters the freezer somewhere through a hole you have to drill through its side. A coil on the inside ensures that the water remains inside for a certain amount of time. The longer the coil, and the slower you flow the water, the better cooling effect you will get.
Another hole needs to be drilled through the side for the tube to exit again. Water is pumped through the tube by means of a very small pump, maybe even a small power head pump. Alternatively, use water from a bypass on the main water return line, the one going back to the aquarium. This will require that you glue a Tee-fitting in-line, and then bush it down to the size of the tube (hose) that you are using. After you have passed the coil through the holes you drilled, isolate the inside of the unit by applying a liberal amount of aquarium silicone around the holes, both inside and outside the freezer.
Because certain types of material inhibit heat exchanges, e.g. plastics, the best cooling effect is obtained with stainless steel tubing. You must use 316 SS, as other types will not resist salt water for very long. Copper can, of course, not be used. Another metal that is safe, but much more expensive, is titanium.
Since you are pushing warm water through the freezer unit all the time, it will run just about continuously. This is a major consideration in terms of electric consumption.
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