I should've said - when I was a kid, I kept some Giant African snails in an old fish tank - using a fish tank thermostat & a screw-fit light bulb (probably 60W) as the heater. It kept a steady 25 degrees C, in a very cold house, being on about quarter of the time, I think - hence observations on heat!
When I accidentally left the thermostat out of the tank, they got cooked as the bulb stayed on continuously. That was the end of my snail-keeping!