Ambient heat only is the best

[DennisM]

I should also mention that I had my oil heater running for about 2 months, in addition the heat tape, before I went with ambient heat only. I wanted to make sure that I could control the ambient temps, before I solely relied on them.

good move, which also happens to be option #3. some folks do this as a permanent setup. bring ambient up to a certain point and then supplement as needed. I can see where this would be an especially useful approach for a collection that contains assorted species with differing heat requirements.