You need to provide your bearded dragon with external heat due to the fact that he's cold-blooded.
  If he can't properly regulate his body temperature, he will be unable to fend off diseases and digest food properly.
  There are a few things you need to know about providing bearded dragon heating.
  This article will tell you everything you need to know.
You can't have the temperature the same throughout the whole terrarium.
  You have to set up a temperature gradient.
  The warmer sides needs to be anywhere from the mid 80s to the mid 90s.
  The cooler side should be between the mid 70s and mid 80s.
Bearded dragons love to bask in the sun in the morning to heat themselves up.
  Therefore, it's important that you setup a basking area.
  If you have an adult, this area should have a temperature between 100 and 105 degrees Fahrenheit.
  If you have a juvenile, you can have the maximum temperature up to 110 degrees.
Obviously in the wild, the temperature drops whenever the sun goes down.
  Therefore, the nighttime temperature in the cage needs to be cooler than the daytime temp.
  It should ideally be in the low 70s.
  One of the best options is to use a ceramic heat bulb to provide the necessary heat at night.
  Unlike other bulbs, it won't emit much light while producing heat.
It's very important that you monitor the temperature in the cage.
  You don't want your bearded dragon to be too cold or too hot.
  You should invest in a few quality thermometers.
  Place the thermometers as close to the area that you wish to monitor.
  If it's too far apart, you will probably get an inaccurate reading.