As described in the previous section, a wild bearded dragon will spend a lot of its time basking. During this period, the dragon is exposed to plenty of warmth and UVB. This species will bask for a long time during the day, but won't be out for quite as long at noon when the heat and UVB are at their strongest.
To aid in deciding which intensity of UVB is required for each species, UVI readings have been taken in their natural habitat. These readings are compiled over time to get an average exposure reading, which sits in one of 4 distinct ranges called Ferguson zones. Zone 1 animals get very little UVB exposure, Ferguson Zone 2 consists of partial baskers, Zone 3 is basking reptiles and Zone 4 animals bask in UVB-intense environments. Bearded dragons are recorded as basking in Ferguson zone 3 (UVI 1.0-2.6).
In the same way, we allow a little variance in the temperature of the basking spot, we would not worry too much if the UV exposure is a little too strong at the closest point. As long as there is a gradient present, the bearded dragon will place itself in the perfect position.
UV tubes are currently available in 2 sizes, T8 and T5. The T8 lamps are around 1 inch in diameter; they must be replaced every 6 months or so, and they have an effective range of 9-12 inches. T5 lamps are the newer iteration. They are around half an inch in diameter, they must be replaced every 12 months and have an effective range of 18-24 inches.
If the enclosure is 2ft tall as recommended, we would advise using a T5 unit and for this species a Zone 3, 10% or 12% UVB tube. When mounted around 30cm from the main basking spot, these UVB tubes should provide the correct basking zone. The UVB unit should be mounted to the ceiling close to the back wall. This configuration will provide a nice UV gradient from the back of the enclosure towards the front and from the top of the enclosure to the bottom. With the UV and basking lamp set up this way, we achieve a temperature gradient along the width of the enclosure and a UV gradient along the depth of the enclosure. This means that whatever the dragon's requirements are, they can find the perfect position within the enclosure.
Though the bearded dragon is a basking species, it may desire some time during the day in an area with little to no light. To allow this, we advise providing partial and full hiding spots throughout the enclosure.