Reptile UVB lighting
For most reptiles and birds, the best choice is a linear T5 High Output (HO) fluorescent tube in a reflector fixture. Match the bulb strength (roughly 5-7% for forest and shade species, 10-12% for desert and open-sun species) to your pet's Ferguson Zone and the distance to the basking spot.
Which UVB light does what
- Linear T5 HO FluorescentConsistent, wide-coverage UVB radiationUse as the main UVB source for almost all day-active and crepuscular reptiles and indoor birds, in most enclosure sizes.Amazon ↗
- Linear T8 FluorescentLow-intensity linear UVB outputUse only in short enclosures or for shade-dwelling species that need low UVB close to the lamp.Amazon ↗
- Compact / Coil BulbsavoidNarrow, uneven patch of UVBNot recommended. They light only a small patch and fade quickly, so a linear tube is a better choice even in small enclosures.
- Mercury Vapor Bulbs (MVB)Combined heat and UVB outputUse for very large or tall enclosures, such as for big tortoises, that need intense heat and UVB from one high-mounted fixture. Never put one on a thermostat or dimmer; it needs full power and a cool-down before it restarts.Amazon ↗
- UVB LED BulbsavoidNewer, less-tested UV outputNot yet a safe default. Few models have independent UV testing, so stick with linear fluorescent tubes unless a specific product has published UV index data.
Sizing: Choose a linear T5 HO fixture that spans roughly 1/2 to 2/3 of your enclosure's length. Position it so the basking spot gets the target UVI, allowing for about a 30% to 50% loss if it shines through a mesh top. A UV index meter is the only way to know for sure.
What each animal's guide calls for
From the checklists on each care guide, so this table and those pages always agree.
- Bearded dragonT5 HO UVB Light Fixture and 10.0/12% TubeT5 HO 10-12% linear desert bulb spanning 1/2 to 2/3 of enclosure length$60–$90
- Ball pythonLinear T5 UVB KitLinear T5 HO Ferguson Zone 1-2$40–$70
- Leopard geckoLow-Output Linear T5 UVB Kit (2.5%-7%)Low-output 2.5-7% T5 linear tube$45–$70
- Corn snakeLinear T5 HO UVB Kit (5-6%)T5 HO 5-6% linear tube$45–$70
- Red-eared sliderT5 HO UVB Light Fixture & BulbT5 HO 10-12% linear tube$60–$110
- BudgieFull-spectrum UVA/UVB avian lightrecommended$35–$70
- Crested geckoLow-Output Linear T5 UVB Kit (7%)Low-output 2.5-7% T5 linear tube$40–$65
- LovebirdAvian linear UVB lamp fixturerecommended$35–$70
- Veiled chameleonT5 HO UVB Light Fixture and BulbT5 HO 6% or 10.0 linear tube spanning 1/2 to 2/3 of top ceiling mesh$45–$75
- Green-cheeked conureAvian UVB Lamp KitAvian-specific 2.4% UVB linear lamp mounted over the cage on a daytime timer$40–$75
- Russian tortoiseT5 HO Linear UVB Light FixtureT5 HO 10-12% linear tube fixture covering 1/2 to 2/3 of enclosure length$50–$80
- CockatielAvian Linear UVB Light Kitrecommended$35–$70
- Blue-tongue skinkT5 HO UVB Fixture and 10-12% BulbT5 HO 10-12% linear tube covering 1/2 of the enclosure length$70–$120
- Sulcata tortoiseT5 HO UVB Light Fixture KitT5 HO 10-12% linear tube covering 1/2 of the indoor enclosure length$60–$90
- Box turtleT5 HO 6% or 5.0 UVB Fixture and TubeT5 HO 6% or 5.0 linear tube over the warm half$70–$130
- Zebra finchAvian Full-Spectrum UVB Light FixtureFull-spectrum avian UV lamp$35–$75
- Pacman frogLinear T5 UVB Kit (2.4-6%)Linear T5 HO 2.4–6%$40–$65
- Green iguanaT5 HO Fixture and 12% UVB Tube (48 in)T5 HO 12-14% desert-strength tubes$160–$280
- ParrotletAvian Full Spectrum UVB LightAvian-specific 2.4% UVB linear lamp mounted over the cage on a daytime timer$40–$75
- White's tree frogLinear T5 HO UVB KitLow-output UVB$40–$70
- Boa constrictorT5 HO UVB Light Fixture KitT5 HO 5-6% linear tube covering 1/2 of the enclosure length$70–$130
- CanaryAvian full-spectrum UVB light unitLinear full-spectrum avian UVB fluorescent light$40–$75
- Gargoyle geckoLinear T5 UVB fixture & bulbLow-output T5 tube$50–$80
- Argentine tegu48-inch T5 HO UVB Fixture and 10-12% TubeT5 HO 10-12% linear tube$80–$150
- Hognose snakeT5 HO UVB Light Fixture & Bulb (5-6%)T5 HO 5-6% linear tube covering 1/2 to 2/3 of enclosure length$45–$70
- Musk turtleT5 HO Linear UVB Fixture & 5.0 BulbT5 HO 5.0 / 6% linear tube lamp spanning 1/2 of tank length$45–$75
- KingsnakeLinear T5 UVB Kit (5-6%)Recommended: T5 HO 5.0 or 6% linear tube$40–$70
- Milk snakeT5 HO 5.0/6% Linear UVB KitRecommended: T5 HO 5.0 or 6% linear tube$45–$70
- African fat-tailed geckoLinear T5 UVB KitLow-level T5 HO linear UVB$40–$70
- UromastyxT5 HO UVB Fixture with 12-14% TubeStrong T5 HO 12-14% linear tube$60–$110
How to choose
- 01Identify your animal's Ferguson Zone and target UV IndexEach zone sets a UV Index (UVI) range: about 0-0.7 in the shade up to 0.7-1.4 at the brightest spot for Zone 1, 0.7-1.0 up to 1.1-3.0 for Zone 2, 1.0-2.6 up to 2.9-7.4 for Zone 3, and 2.6-3.5 up to 4.5-9.5 for Zone 4. Aim for the higher number at the basking spot, with less elsewhere.
- 02Select the bulb percentage based on habitat classForest and shade-dwelling species usually need a 5% to 7% bulb, while desert and open-sun species usually need 10% to 12%. Distance matters as much as the percentage.
- 03Calculate fixture placement and distanceUVB drops quickly with distance, and mesh tops can block about 30% to 50% of it, so set the distance to reach the right UVI at the basking spot.
- 04Plan fixture coverage across the enclosureThe lamp should span 1/2 to 2/3 of the enclosure's length so the animal can move between strong UVB and shade.
Common mistakes
- Using compact screw-in or coil bulbs, which light only a narrow cone instead of a useful gradient.
- Mounting a strong T5 HO bulb too close to the basking perch, which can cause eye damage and skin burns.
- Forgetting that screen tops block UVB. Fine mesh can filter out 30% to 50% of the output.
- Waiting for the bulb to burn out before replacing it. UVB output fades long before the visible light does.
- Not giving enough shade, which prevents the animal from controlling its own UV exposure.
Questions people ask
How often should I replace my reptile UVB bulb?
Replace linear T5 HO tubes about every 12 months, and T8 or compact bulbs about every 6 months, or follow the maker's schedule. The bulb keeps glowing after its UVB output has faded, so you can't judge it by eye.
Does glass or plastic block UVB light?
Yes. Ordinary glass and most clear plastics block nearly all UVB. Never place a UVB fixture over a glass lid or rely on sunlight through a window.
How much UVB light passes through a mesh screen top?
Most terrarium mesh blocks roughly 30% to 50% of the UVB. If your lamp sits on top of mesh, use a stronger bulb or a higher basking spot to make up for the loss, and check with a UV meter if you can.
What is the difference between 5.0 and 10.0 UVB bulbs?
A 5.0 (5-7%) bulb gives lower UV intensity for forest and shade-dwelling species. A 10.0 or 12% bulb gives stronger output for desert and open-sun baskers. Either can be too strong if mounted too close.