A complete reference to UVB lighting for reptiles — covering Zoo Med, Arcadia, and Zilla product lines with specs, species recommendations, and tips to get it right.
Most diurnal reptiles need UVB light to synthesize Vitamin D3, which is essential for calcium absorption and bone health. Without it, reptiles develop Metabolic Bone Disease (MBD) — a painful, often fatal condition. UVB also improves appetite, activity levels, and reproductive behavior.
UVB (ultraviolet B) is a portion of the sun's spectrum with wavelengths of 280–315nm. Reptile skin uses UVB to convert a precursor into Vitamin D3 — the same process that happens in human skin in sunlight.
T5 bulbs are 5/8" in diameter, T8 bulbs are 1" wide. T5 HO (High Output) bulbs are significantly more powerful, cover more distance, and are the current standard for serious keepers. T8 works well for smaller enclosures and lower-UVB species.
The UVB % rating (5.0, 10.0, 6%, 12% etc.) is a measure of the amount of UVB output relative to visible light. Higher percentages are for desert species with intense UV needs. Lower percentages are for forest or shade-dwelling species.
A standard wire mesh screen lid will reduce UVB output by approximately 30–50% depending on the mesh type. If your bulb sits on top of a mesh lid, you must compensate by either using a higher output bulb or placing the bulb closer to the basking spot.
UVB intensity follows the inverse square law — doubling the distance reduces UVB to one quarter of its strength. Always measure the distance from the bulb to the basking surface. A few inches makes a huge difference in actual UVB received.
UVB bulbs lose effective output long before they stop glowing. Most manufacturers recommend replacement every 6–12 months. Zoo Med guarantees output for up to 18 months on some bulbs. Arcadia recommends annual replacement for all lamps.
The original and most widely available reptile UVB brand. Zoo Med invented the first UVB lamp for reptiles in 1993. Their ReptiSun line remains the industry standard, trusted by zoos and veterinarians worldwide. Bulbs are made in Germany.
| Bulb Name | Type | UVB Output | UVB Strength | Max Effective Distance | Best For | Replace Every |
|---|---|---|---|---|---|---|
|
ReptiSun 2.5 UVB
T5 HO Linear
|
T5 HO | 2.5% | 6–8" | Forest Snakes, nocturnal geckos, amphibians that benefit from low UVB | 12 months | |
|
ReptiSun 5.0 UVB
T8 Linear — Most popular T8
|
T8 | 5.0% | 10–12" | Forest Turtles, tortoises, iguanas, tropical lizards, chameleons | 12 months | |
|
ReptiSun 10.0 UVB
T8 Linear
|
T8 | 10.0% | 12–16" | Desert Bearded Dragons, Uromastyx, Tortoises, desert lizards | 12 months | |
|
T5 HO ReptiSun 5.0 UVB
T5 High Output — Upgrade from T8 5.0
|
T5 HO | 5.0% | 12–18" | Forest Chameleons, tropical geckos, water dragons — larger enclosures | 12 months | |
|
T5 HO ReptiSun 10.0 UVB
T5 High Output — Top of Zoo Med line
|
T5 HO | 10.0% | 18–24" | Desert Bearded Dragons, Uromastyx, large desert tortoises, tall enclosures | 12 months | |
|
ReptiSun 5.0 Compact
Coil / CFL — fits standard sockets
|
Compact | 5.0% | 6–8" | Forest Small enclosures only. Linear bulbs are preferred for most setups. | 6 months | |
|
ReptiSun 10.0 Compact
Coil / CFL — fits standard sockets
|
Compact | 10.0% | 8–10" | Desert Small desert enclosures. Linear T5 preferred when possible. | 6 months |
A UK-based brand widely regarded as the premium choice among serious hobbyists and professional keepers. Arcadia bulbs are manufactured in Germany to tight specifications and are favored for their accuracy, longevity, and strong output. Their ProT5 fixture system is highly regarded.
| Bulb Name | Type | UVB Output | UVA Output | UVB Strength | Min Distance (no reflector) | Best For | Replace Every |
|---|---|---|---|---|---|---|---|
|
D3 6% UVB T5 HO
Forest / Tropical — Entry level Arcadia
|
T5 HO | 6% | 30% | 10–12" | Forest Chameleons, crested geckos, day geckos, tree frogs, snakes with low UVB needs, tropical tortoises | 12 months | |
|
D3+ 12% UVB T5 HO
Desert — Most popular Arcadia bulb
|
T5 HO | 12% | 30% | 12–16" | Desert Bearded Dragons, Blue-tongued Skinks, Uromastyx, Mediterranean tortoises, water monitors | 12 months | |
|
Dragon 14% UVB T5 HO
Extreme desert — highest output in line
|
T5 HO | 14% | 30% | 16–18" minimum | Desert Large Bearded Dragon enclosures, Chuckwallas, Uromastyx in tall enclosures — requires careful positioning | 12 months |
Zilla is a widely available budget-friendly brand commonly found at pet store chains. Their UVB products are generally entry-level and best suited for beginners or species with modest UVB requirements. Their Desert 50 coil bulb is a popular pick for bearded dragon starter kits.
| Bulb Name | Type | UVB Output | UVB Strength | Distance at 12" | Best For | Replace Every |
|---|---|---|---|---|---|---|
|
Tropical 25 UVB
T8 Linear or Coil — tropical species
|
T8 Coil | ~25 µW/cm² | 25 µW/cm² | Forest Iguanas, water dragons, tropical geckos, tree frogs, corn snakes | 12 months | |
|
Desert 50 UVB
T8 Linear or Coil — desert species
|
T8 Coil | ~50 µW/cm² | 50 µW/cm² | Desert Bearded Dragons, Leopard Geckos, Tortoises, desert lizards — smaller enclosures | 12 months | |
|
Pro Series UVB Coil
Higher output coil — advanced Zilla line
|
Coil | High | Higher than standard | Desert Bearded dragons, Uromastyx — high UVB species in smaller enclosures | 12 months | |
|
Mini Compact UVB (Tropical)
6W G9 socket — for small kits
|
Mini Coil | Low | Low | Forest Small starter kits only. Very limited coverage. Upgrade when possible. | 6 months | |
|
Mini Compact UVB (Desert)
6W G9 socket — for small kits
|
Mini Coil | Low | Low | Desert Small starter kits only. Very limited coverage. Upgrade when possible. | 6 months |
Use this as a starting point. Always verify output with a Solarmeter and consult a reptile vet for your specific animal's needs. Distances assume no mesh between bulb and animal.
Standard wire mesh screen lids reduce UVB penetration by approximately 30–50%. This means a bulb rated for 18" of effective distance may only be effective to 10–12" when placed over mesh. If your enclosure has a mesh top, always use a higher output bulb than the base recommendation, or mount the bulb inside the enclosure where possible. Arcadia and Zoo Med both document this in their product guides.
UVB bulbs continue to emit visible light long after their UVB output has dropped to ineffective levels. Your reptile can appear to bask normally under a "dead" UVB bulb. Always replace on a schedule — every 6 months for coil bulbs, every 12 months for linear T5/T8 bulbs.
Distance is measured from the surface of the bulb to the top of your reptile's basking spot — not to the floor of the enclosure. A raised basking rock or branch significantly changes the effective distance. Remeasure every time you rearrange the enclosure.
Standard glass blocks virtually all UVB radiation. Never place a UVB bulb on the outside of a glass terrarium and expect UVB to penetrate. Bulbs must be inside the enclosure or over an open mesh top to be effective.
Just like a temperature gradient, provide a UV gradient in the enclosure. The UVB bulb should cover roughly half the enclosure — the basking side — so your reptile can move in and out of the UVB zone as needed. Never illuminate the entire enclosure uniformly.
The only accurate way to measure UVB at the basking spot is with a Solarmeter 6.5 UVI meter. This removes all guesswork from distance, mesh, reflector, and bulb age variables. It's an investment but invaluable for serious keepers. UVI targets: 1–3 for forest, 3–6 for desert species.
A quality reflector — like the one included with the Arcadia ProT5 — can nearly double the effective UVB reaching your reptile compared to the same bulb without a reflector. Always use a fixture with a reflector for maximum efficiency. Never run a T5 bulb without one.
Nothing beats unfiltered natural sunlight. Even 30 minutes of outdoor time in direct sun (no glass or screen between) provides more UVB than hours under a lamp. When weather and safety permit, supervised outdoor time is the gold standard for diurnal reptiles.
Nocturnal species like ball pythons, leopard geckos, and most colubrids do not strictly require UVB. Some species may benefit from low-level UVB exposure but never require desert-intensity levels. Research your specific species before investing in high-output lighting.