A bearded dragon needs a T5 HO UVB tube, such as an Arcadia Desert 12% or Zoo Med ReptiSun 10.0, giving a UVI of 4.0–4.5 at the basking spot. Mount it about 11 in above the basking spot through a mesh top, or 16–17 in with no mesh. Run it 12–14 hours a day and replace it every 12 months, because UVB output fades long before the visible light does.
As an Amazon Associate we earn from qualifying purchases. Links to Amazon below are affiliate links.
Why bearded dragons need UVB
Bearded dragons make their own vitamin D3 in their skin when it is exposed to UVB, and they need D3 to absorb calcium. The Washington State University veterinary hospital lists inadequate UVB and a lack of vitamin D3 among the common causes of metabolic bone disease. Its signs include weak legs, a soft or swollen jaw, tremors and fractures, and juveniles are the most vulnerable.
In the wild they bask in open sun. The UV-Tool (Baines et al., 2016), a widely used guide to UV lighting in captivity, places Pogona vitticeps in Ferguson zones 3–4. Those are open-sun baskers, with a peak UV index of roughly 3 to 9.5 in the sunniest spot. That is why a bearded dragon needs a strong tube and a gradient, from a high UVI under the lamp to near zero in the shade.
UVB bulb types compared
| Bulb type | UVB strength | Lifespan | Verdict |
|---|---|---|---|
| T5 HO linear tube (10–14%) | High; reaches the basking spot at 11–18 in | About 12 months | Best choice for most enclosures |
| T8 linear tube | Low; too weak through a mesh top | 6–12 months | Not recommended for bearded dragons |
| Mercury vapor (self-ballasted) | High; also gives heat | About 12 months | An option; keep it at least 10 in from your dragon |
| LED UVB | Unproven | Unknown | Avoid for now |
The T5 vs T8 comparison follows Zen Habitats and the UV-Tool, which notes that T5 HO tubes and some mercury vapor lamps produce far more UVB than T8 tubes. Lifespans are from ReptiFiles and Arcadia. ReptiFiles says LED UVB “isn’t ready for safe use with reptiles yet.”
UVB distance chart
These are the distances from the tube to the top of the basking spot that give a UVI of about 4.0–4.5, with the tube in a reflector fixture.
| Bulb | Over mesh | No mesh (inside the enclosure) |
|---|---|---|
| Arcadia Desert 12% T5 HO | 11 in (27 cm) | 16–17 in (40–42 cm) |
| Zoo Med ReptiSun 10.0 T5 HO | 11 in (27 cm) | 16–17 in (40–42 cm) |
| Arcadia Dragon 14% T5 HO | 11–12 in (28–30 cm) | 17–18 in (43–45 cm) |
| Arcadia 100W mercury vapor | Not given | 12 in gives UVI 6; 16 in gives UVI 4. Never closer than 10 in |
T5 distances are from ReptiFiles and assume an Arcadia fixture and a mesh that blocks about 45% of UVB. The mercury vapor figures are Arcadia’s, which say a mesh top cuts its output and range by about 30%. Without a UV meter, add 1–3 in to allow for your dragon’s height on the platform.
How to set up UVB
- Pick the length. The tube should light your dragon’s whole body when it basks. A 22 in tube suits a 4×2 ft enclosure. Mount it on the warm side, next to the basking lamps.
- Use a reflector fixture. A reptile T5 HO fixture with a reflector, such as Arcadia’s, is what the distances above assume.
- Keep glass and plastic out of the way. Ordinary glass and plastic block UVB almost completely. The UV-Tool measured 0.4% transmission through 4 mm window glass, so never put a cover or a sheet of glass between the tube and the dragon.
- Set the height. Raise or lower the basking platform until its top sits at the distance in the chart.
- Leave a shade side. The UVI should fall to near zero at the cool end, with hides there, so your dragon can choose how much it gets.
- Put it on a timer. The UV-Tool lists a 13–14 hour summer day for Pogona vitticeps, and 12–14 hours suits most homes.
- Measure if you can. ReptiFiles recommends the Solarmeter 6.5 and no other meter for reading UVI. Check the basking spot when the tube is new, then regularly, as the UV-Tool advises.
Hypomelanistic, translucent and silkback morphs are more sensitive. ReptiFiles advises keeping their basking UVI at 3.0 or lower, so set the tube higher or use the 12% rather than the 14%.
For heat and the rest of the build, see the enclosure setup checklist. Pair UVB with the calcium schedule in our food guide, since a dragon needs both to build bone.
When to replace a UVB bulb
- T5 HO tubes: every 12 months for most good brands, according to ReptiFiles. It says Exo Terra tubes need replacing every 6 months.
- Mercury vapor: every 12 months, according to Arcadia.
- T8 tubes: every 6–12 months, per Zen Habitats, though we don’t recommend them.
Write the install date on the tube or the fixture. A tube that still glows can give little UVB: the UV-Tool found lamp output falls as the glass ages, and one product lost 64% of its UV index within 1,000 hours. Our care guide puts the yearly tube change in its routine.
UVB lights we would buy
- Best overall: Arcadia ProT5 Desert 12% kit. Tube, reflector and fixture together. The 22 in kit suits a 4×2 ft enclosure.
- Replacement tube: Zoo Med ReptiSun 10.0 T5 HO. Same distances as the Arcadia 12%. Use it in a reflector fixture.
- Tall enclosures: Arcadia Dragon 14% kit. For tall enclosures such as 4×2×4 ft or 6×3×3 ft, where Zen Habitats suggests a stronger tube.
- UV meter: Solarmeter 6.5. Shows the actual UVI at the basking spot and tells you when a tube is spent.
- Mercury vapor option: Arcadia D3 UV Basking Lamp. UVB and heat from one dome lamp. Arcadia says to keep it at least 10 in from your dragon.
Common UVB mistakes
- Running a tube until it burns out. UVB fades long before the light does. Replace it on schedule.
- A T8 tube on top of a mesh lid. Too little UVB gets through to the basking spot.
- Using the no-mesh distance over mesh. The tube has to sit about 5–6 in closer when it shines through a screen.
- Lighting through glass. A glass lid, or a dragon basking by a closed window, gets almost no UVB.
- No shade. Covering the whole floor in strong UVB leaves your dragon no way to avoid it.
Bearded dragon UVB FAQ
What UVB is best for a bearded dragon?
A T5 HO tube in a reflector fixture, such as the Arcadia Desert 12% or Zoo Med ReptiSun 10.0, aimed at a UVI of 4.0–4.5 at the basking spot.
How far should a UVB light be from a bearded dragon?
For an Arcadia 12% or ReptiSun 10.0 T5 HO, about 11 in above the basking spot through a mesh top, or 16–17 in with no mesh, according to ReptiFiles.
Is 10.0 or 12% UVB better for bearded dragons?
Either works. ReptiFiles gives the same distances for both. Use a 14% tube only when the basking spot sits further from the lamp, as in a tall enclosure.
Should the UVB light be on at night?
No. Run it 12–14 hours a day on a timer and switch it off at night with the other lights.
How often should I replace a bearded dragon UVB bulb?
Every 12 months for most T5 HO tubes and mercury vapor bulbs, even if they still light up. ReptiFiles says Exo Terra tubes need replacing every 6 months.
Does UVB go through glass?
No. Ordinary glass and most plastics block almost all UVB, so a lamp must shine directly or through mesh, and window sunlight doesn’t count.
Sources
- ReptiFiles: Bearded dragon lighting, heating and humidity
- Baines et al. (2016), How much UVB does my reptile need? The UV-Tool. Journal of Zoo and Aquarium Research 4(1): 42–63
- Washington State University Veterinary Teaching Hospital: Metabolic bone disease in bearded dragons
- Zen Habitats: Best UVB bulbs for bearded dragons, T5 vs T8
- Arcadia 100W Mercury Vapour D3 Basking Lamp: product specifications
More guides: enclosure size and setup, care, food and feeding schedule, substrate, where to buy a bearded dragon.