UVB lighting explained

Why UVB matters

Reptiles use UVB light to make vitamin D3, which lets them absorb calcium. Without the right UVB, many species develop metabolic bone disease: soft, weak and deformed bones. Even species once thought not to need it, like many geckos and snakes, benefit from low levels.

What UVI means

UVI (UV index) measures the strength of UVB your reptile actually receives. It depends on the bulb, how far away it is, and whether there's mesh in between. Mesh can block a big share of the light, so the bulb has to be closer.

The most reliable way to check is with a UV meter such as a Solarmeter 6.5. Without one, follow the manufacturer's distance guidance for your exact bulb and setup.

How much each species needs

These are the targets at the basking spot from our care sheets. Shade and cool areas should have less, so your reptile can choose.

Getting it right

• Use linear T5 tubes for most species. They spread UVB across a wider area than compact bulbs.
• Never put glass or plastic between the bulb and the animal: it blocks UVB.
• Run UVB on the same day cycle as the main lights, usually 10 to 14 hours.
• Replace T5 UVB tubes about every 12 months, even if they still light up. UVB output fades long before the visible light does.
• Albino and other low-pigment animals need lower levels.