Being cold-blooded animals, bearded dragons in captivity need proper lighting to provide heat and regulate their body temperature. Temperature is very important to the well-being of a bearded dragon. This brings us to a common question which is whether the heat bulb in your pet’s tank should be turned on or off over night.
The straight answer to this is; it really depends on the overall heating arrangement in the housing of your pet.
There are different heating equipments that you can install on your pet’s vivarium. If your heat bulb is only providing a hot spot for basking and there are under tank heat mats, ceramic heaters, hot rocks or similar providing a general warm background temperature then, yes, it can probably be switched off over night. In fact there is a good deal of evidence to suggest that a night-time temperature drop can be very beneficial with a whole range of reptiles, especially if you’re planning to breed. The idea behind it is pretty obvious really. Come sun down, even in the tropics the temperature drops so mimicking this in the vivarium allows animals to experience as natural a day/night cycle as possible. How much you allow the temperature to drop obviously depends on the animals concerned. Desert temperatures plummet once the night falls, but for bearded dragons, around 5 degrees C should be about right.
On the other hand, if the heat bulb is the only source of heat in the tank, then switching it off is more problematic and you might want to think about changing your set up to allow you to maintain the ambient temperature by other means.