LynnThank u, as always ur input is greatly appreciated. I was considering the Exo terra cable but had not seen many testimonials about it. But it sounds like it might b a winner what size are your tanks? As far as how many does it stretch over collectively? Did it cause the upper level of the tank in your case to get to warm? That's one of my main concerns. Or would a timer be in order. To turn it on every so often to regulate a small fluctuation? I guess trial an error is in order to really find out. Someone suggested a small heater In the room with a thermostat that turns the heater off when a desired temperature has been met. My RETF always seem to do so well. We have a good routine. Hope I did not just jinx myself. Knock on wood, lol.