Hi, supplementary nighttime heat depends on the ambient (air) temp in the room the enclosure is in.
The lowest ambient temp I would recommend is between 21 to 24c (72 to 75f). If you do need to add a heat bulb, either an infrared bulb, or a ceramic heat emitter are fine.
The infrared emmits a little light as well as heat, the ceramic heat only. So long as your monitor has hiding places, the light from the infrared should not disturb the animal at all.