I have had a cold-water-only installation and have used aquarium heaters
sucessfully for my water jacket. I used an aquarium circulator for evenly
distributing the heated water and still do. Cost for the circulator was
less than 11 dollars, My shop had NO hot water and this was an amazingly
accurate workaround; be advised that these heaters give off light! Seems
this is a feature....
All of this stuff requires reasonable monitoring with a vanilla Weston
thermometer, but of course it works. I've only been trying to stay around
68 farenheit for black and white, so this whole gag may be nonesense for
colour, but at least the colour temps will let you cook british columbia
prawns consistently.
Actually Rusty Atkins has a reasonable idea, and I can confirm that it
works. Sorry that I can't flame anyone or deliver a magestic pompous
theoretical expensive opinion.
Let light through the lenses!
-Mike