UVB and heat lamps for tortoises
Why tortoises need UVB and a basking lamp, the difference between tubes and mercury vapour bulbs, how high to hang them and when to replace them.
Tortoises need two things from the sun: heat to run their body, and UVB to make vitamin D3 so they can use calcium. Window glass blocks UVB, so a tortoise by a sunny window still isn't getting any.
Two ways to do it
| Set-up | Good for | Watch out for |
|---|---|---|
| Combined bulb (mercury vapour: heat + UVB) | Simple tables, young tortoises | Fixed wattage: adjust height to get the temperature right. Needs a ceramic holder. |
| Basking bulb + UVB tube (T5 10–12%) | Bigger tables, adults | Two fittings. Tube should cover about half the table. |
How high?
Follow the maker's distance for UVB. For heat, measure: under the lamp at shell height you want 30–35 °C. Too hot? Raise it or use a lower wattage. Too cool? Lower it, but never closer than the manufacturer allows. Keep bulbs out of reach so the tortoise can't climb up to them.
When to replace
UVB fades long before a lamp stops lighting. Replace on the manufacturer's schedule, usually every 6–12 months. Write the date on the base with a marker when you fit it.
Safety
- Use ceramic lamp holders, not plastic.
- Keep lamps away from flammable bedding and curtains.
- A guard or cage over the bulb stops climbing tortoises touching it.
Checked November 2026. General information, not veterinary advice.