It´s recommended that you keep the lights on from 10 to 12 hours, in the summer months. In the winter months you can shorten this to 8 to 10 hours a day. This is to simulate the length of the days in the different seasons.
Giving of UV light (ultraviolet radiation) to bearded Dragons is extreme importance (just like whit many other reptiles and amphibians). In the wild, the bearded dragon captures the UV radiation from the sun. A distinction is made between UV-A, UV-B and UV-C. The bearded dragin mostly needs UV-B.
UV light stimulates the reproduction, feeding behavior and growth of a bearded dragon, and is indispensable in a terrarium. UV light is necessary to better absorbe vitamin A and D. It also helps creating Vitamin D3. Vitamin D3 is needed for the absorption of calcium in the bones. Calcium is necessary for a good strong and healthy bone structure.
When UV lighting is missing from the housing (particularly whit young animals), can cause serious health problems. The young animals start to vibrate, they grow poorly (while they have plenty of food) and get adhesions. To result in serious joint and skeletal problems and deformities.
There are special uv lights you can buy for terrarium. For best results, you need the lamp up to 45 cm above the bearded dragon and it´s recommended to keep it on to 10 to 12 hours a day. This lamp must be replaced every year (even though the lamp is not yet broken). Please notice that UV light gan not get through glass or plastic.
Avoid any that no UV lighting is present, then it is necessary to the bearded dragons regularly (at least 3 times a week for half an hour) to offer direct sunlight. This is very important for growing bearded dragons. Unfortunately, it is not always possible to give the animals to direct sunlight.