I have though about this for different reasons. Over time I get hard water buildup on my circulator and have to spend some time cleaning. Yeah, I could use distilled, but it's a pain. Not only that but over time the water evaporates, especially at higher temps and I have to keep refilling which drops the temp for a bit. I know there are "ping pong" balls you can place in the water to keep the surface area to a minimum. My current solution is to simply make a tin foil lid.<p>But if I could find another medium to use instead of water it would be nice.