I do 2 carboys at a time soaked in a large platic bin of water. I keep the temperature set to within one degree using an aquarium chiller. The pumps in the water that push the water to the chiller generate heat so I have not need a heater here in california.
With this method I was able to ferment a marzen at 55 degrees when the garage was at 95. ATM im doing a brown ale at 61 degrees and the garage is in the 40-50s.


