Red light can disturb their sleep. If the overnight temperatures stay above 65 in the tank, I wouldn't use any night heating at all. They are fine down to around that temperature. If it gets colder than that, I would use a ceramic heat emitter which will provide some heat but no visible light. I use a 100w ceramic heat emitter in the winter mounted 25'' above the floor of the tank and it keeps the temps in the mid 70s. You could use a lower watt emitter at a closer distance for the same effect. That depends on your setup.