I have looked at them. I uses a Peltzer(sp?)junction cooler. An electric current applied to the exchanger causes one side to cool and the other side to heat. The fan is to cool the side that heats up. They require a DC power supply (usually provided separately. However the BTU rating is small. I contacted the company about use on a 58 gallon tank and was told that a single unit would only make a 1-2 degree temperature drop. I even looked at buying just the exchanger and mounting several on my sump but the cost, power requirements, and heatsink requirements did not make it attactive. IMO for now they have a place in water coolers and other similiar applications but not ready for large cooling applications.
