I have a thermoelectric chiller / heater that is perfect for your nano. It goes up to about a 45 or 50 gallon aquarium. This is ver very small and very quiet. When they came out they cost $850, obviously they are cheaper now. I am offering it to you for $135. The company is Azoo and the model # is CH-200. It is an inline chiller. I would have to say the dimensions are 6 " L x 6" W x 10" H. Again, you could barely here it and it has an external power supply for it.