Re: Mann Lake rep here on BSource?
That would be a royal pain in the butt. How do you set two thermostats the same and know which one to raise or lower if that is your choice. If you are going to do something do it right. Get a temperature controller that has hi and low limits on the set point. If one or the other goes outside the set point limits an alarm is indicated. Usually it is a red or green led but you can get them with an audio alarm or wire one up. Then your process is in control and if it isn't you are warned.
That is why I suggested oil instead of water.
Of course, if you leave a bottling tank on and unattended for an extended period the water can still evaporate and create a problem.
Zone 5a, Practicing non-intervention beekeeping