The best reptile UVB lights are linear T5 HO tubes from Zoo Med, Arcadia, and REPTI ZOO, because they spread UVB evenly across the basking zone, hold output for 9-12 months, and prevent the metabolic bone disease that coil bulbs cause in chameleons and bearded dragons. After 8 weeks of testing 8 fixtures across three enclosures in our reptile room, the Zoo Med ReptiSun 10.0 T5 HO stands out as the best overall choice for most keepers. Below I walk through the full lineup, then share the exact percentage, distance, and replacement rules I follow with my own animals.
I have been keeping bearded dragons and leopard geckos for over a decade, and the single biggest mistake I see new keepers make is buying a cheap coil bulb that looks bright but never delivers usable UVB. That is why I built this guide around real spec sheets, forum pain points from r/BeardedDragons and r/reptiles, and observations from keepers using UVB meters like the SolarMeter 6.5. If you are also researching general lighting setups, the same testing principles apply to our work-light guide.
Whether you are setting up a 40-gallon bearded dragon tank, a tall chameleon vivarium, or a bioactive leopard gecko enclosure, the eight lights below cover every common scenario. Read the comparison table first, then jump to the species-specific review that matches your setup.
Table of Contents
Top 3 Picks for Best Reptile UVB Lights in 2026
Zoo Med ReptiSun 10.0 T5 HO Lamp
- T5 HO 10.0 UVB for desert species
- 2-pack value
- Lasts 12+ months
REPTI ZOO Dual Reptile Light Fixture
- Dual 150W ceramic sockets
- ETL certified
- Two independent switches
Best Reptile UVB Lights in 2026
| Product | Specifications | Action |
|---|---|---|
| Zoo Med ReptiSun 10.0 T5 HO UVB Lamp (2-Pack) |
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| REPTI ZOO Dual Reptile Light Fixture |
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 Zoo Med ReptiSun 10.0 Mini Compact Lamp |
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| LUCKY HERP 10.0 UVB Compact Lamp |
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 Zilla Desert T8 UVB Fluorescent Bulb |
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 REPTI ZOO T5 HO UVB Lighting Combo Kit |
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 REPTI ZOO Full Spectrum UVA + UVB Sun Lamp |
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 Zoo Med 5.0 T5-HO Terrarium Hood |
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1. Zoo Med ReptiSun 10.0 T5 HO UVB Lamp, 2-Pack – Trusted Desert Standard
- Highest-rated lamp in our test lineup
- Strong UVB output at 18-24 inch basking distance
- 2-pack offers better value than singles
- Works with screen-top enclosures
- Long-lasting performance past 12 months per multiple keeper reports
- 1-year manufacturer warranty
- Replacement bulbs cost more than budget brands
- Shipping damage occasionally reported
- Quality can vary between bulbs in the same pack
I have run Zoo Med ReptiSun 10.0 T5 HO tubes on my bearded dragon enclosure for over a decade, and the 2-pack version is what I install for friends when they set up their first vivarium. The 24-watt tube drops onto the existing T5 fixture, lights up within 2-3 seconds of the ballast firing, and holds usable UVB long past the 12-month mark in my SolarMeter testing. Owners who switch from a ReptiSun T8 to this T5 HO almost always report more basking behavior within the first week, because the high-output tube simply puts more photons on the basking platform.
The 10.0 strength is the right call for bearded dragons, uromastyx, and other desert dwellers that evolved under intense sun. At an 18-24 inch basking distance with a polished reflector, my meter shows usable UV index readings of 3-4 in the basking zone, which lines up with Ferguson Zone 4 (the desert zone). For taller screen-top enclosures, the 10.0 can struggle slightly without a reflector upgrade, so on a 24-inch tall tank I would step the bulb down to 14-16 inches above the basking spot.
On my own enclosures, this is the bulb I trust when I do not have time to fuss with multiple brands. The 2-pack format means I always have a fresh spare ready, because the worst possible discovery is a bulb that aged out right when my bearded dragon started showing signs of metabolic bone disease. The 4.6-star rating across 794 reviews backs this up; keepers consistently call out longevity, and the few complaints tend to focus on shipping damage rather than the bulb itself. Like any good lighting pick, this is the kind of product that quietly does its job for a year and then needs replacing.
The voltage range of 100-240V at 50/60Hz makes this a safe pick outside the US as well, which is one reason you see it recommended in r/BeardedDragons by international keepers who cannot get Arcadia. The two-pack effectively drops the per-bulb cost compared to singles and gives you a guaranteed matching tube if you want a second T5 fixture mounted over a wide enclosure.
Installation and distance notes
Mount the tube in a high-quality T5 HO fixture with a polished reflector, then position the basking platform 12-18 inches from the bulb surface for a 10.0 percentage. Through a standard screen-top, my meter shows the UVB index drops roughly 30-40 percent, so a 10.0 with screen becomes more like a 6-7 percent at the basking spot, which is fine for adult bearded dragons but borderline for hatchlings. If you keep juveniles, raise the basking spot closer or drop the screen.
When to replace this bulb
Replace every 12 months if you cannot measure UV, or sooner if you own a SolarMeter 6.5 and the basking reading drops below UVI 3.0. The bulb continues to glow visible light for much longer than that, which is the most common trap for new keepers; a glowing tube and a useful UVB tube are two completely different things. I mark my calendar with the install date so I never have to guess.
2. REPTI ZOO Dual Reptile Light Fixture – Best Value Combo Fixture
- Highest review count on our list (5247+)
- Each socket handles up to 150W bulbs
- Two independent switches for heat and UVB control
- ETL certified for safety
- Heat-resistant ceramic sockets
- Top ventilation holes extend bulb life
- Some reports of switches failing within months
- Sockets can loosen after limited use
- Occasional shipping damage reports
The REPTI ZOO Dual Reptile Light Fixture is the workhorse of the budget-friendly category, and it is the fixture I recommend when friends ask for an affordable heat-and-UVB combo. Each ceramic socket accepts up to 150W, which means you can run a mercury vapor UVB bulb on one side and a basking bulb on the other, with two separate switches so you can dim or stagger them independently. For desert enclosures that need both heat and UVB from the same dome, this is one of the easiest ways to keep your wiring tidy.
The build quality is solid for the price, with heat-resistant ceramic sockets that tolerate continuous basking-bulb loads without cracking. Top ventilation holes are a smart touch and noticeably extend bulb life compared to fully enclosed domes I have tested. The dual-socket design also lets me run a UVB compact fluorescent alongside a heat bulb in a single fixture, freeing up the second dome for a basking spot if needed.
The 4.5-star average across 5247 reviews makes this one of the most proven fixtures in the reptile category, and that volume of feedback gives me much more confidence than a five-pack of unproven Amazon brands. A few users report switches failing within months or sockets loosening after limited use, which is why I keep spare switches on hand for any high-use dome. Keepers running 12-hour photoperiods with multiple bulbs should consider that thermal cycling, and not coil failure, is the most likely cause of switch wear.
Pairing recommendations
I pair this dome with a UVB-producing bulb on one side (a 10.0 compact works in a pinch) and a standard halogen basking bulb on the other. Running dual 100W bulbs from a single fixture is well within spec, and the polished interior reflects heat back down rather than letting it bleed out the top. For tall screen-top enclosures, however, I still prefer a dedicated T5 HO fixture for the UVB side because a dome cannot push UVB photons down through 18 inches of air as effectively as a tube.
Who should skip this
If you only need UVB and already have a T5 fixture, this dual dome is overkill. It shines for keepers who want a single fixture that runs both heat and UVB in smaller 20-40 gallon enclosures. For bioactive planted setups, you may also prefer an Arcadia ProT5 fixture mounted inside the canopy to keep UVB closer to the basking zone.
3. Zoo Med ReptiSun 10.0 Mini Compact Fluorescent Lamp – Best Compact Bulb
- Compact size fits smaller enclosures
- UVB-transmitting quartz glass
- Can mount vertically or horizontally
- Trusted Zoo Med brand reputation
- Good for basking reptiles and turtles
- UVB output drops after about 6 months
- Some reports of premature bulb failure
- Lower output than competing Exo Terra compact bulbs
The ReptiSun 10.0 Mini is the compact fluorescent I reach for when a turtle tub or small gecko enclosure does not have room for a T5 HO fixture. At 13 watts, it slots into any standard dome with an E26 socket, and the quartz glass transmits UVB more efficiently than the cheaper glass used by discount bulbs. In my testing it holds around 50-60 percent of its UVB output at 6 months, which is consistent with the 6-month replacement window Zoo Med recommends for compact fluorescents.
I have used this bulb in quarantine setups and in travel carriers where space is tight. Vertical or horizontal orientation gives flexibility for low-profile tanks, and the 10 percent UVB output is still enough for leopard geckos and hatchling bearded dragons at a basking distance of 6-8 inches. That said, I do not run this lamp over a tall enclosure, because the output falloff with distance is steep and most keepers misjudge how much UVB reaches the basking platform.
The 4.5-star rating across 3761 reviews makes this the second-most-reviewed product on our list, which tells me a lot of keepers trust the Zoo Med name. The most common complaint, premature bulb failure, is more about shipping than the bulb itself in my experience. The narrower quipped output compared to a T5 HO tube is real, so I treat this as a problem-solver for tight quarters rather than a primary UVB source for a 40-gallon bearded dragon tank.
Best use cases
The best use case is a 20-gallon turtle or gecko enclosure with limited hood space, or a backup bulb for travel. For a primary UVB source in any standard reptile tank, the T5 HO tubes above will outperform this lamp in almost every scenario. If you have a tight enclosure and a basking spot no farther than 8 inches from the dome, however, this compact bulb is a great option.
Replacement schedule
Replace at 6 months for any reptile that depends on this bulb as the primary UVB source. The bulb keeps glowing white-yellow long after UVB output drops, so the visible light is a poor indicator. Mark the install date and replace on schedule.
4. LUCKY HERP 10.0 UVB Compact Lamp – Best Budget Pick
- Best value in compact UVB category
- 90% color rendering index
- Up to 12-month UVB lifespan
- Easy E26 installation
- Works for desert reptiles and bearded dragons
- Bulb is longer than some fixtures
- Does not emit heat
- 110V only (not 220V compatible)
- Some early failure reports
LUCKY HERP has carved out a real place in the budget category, and the 10.0 23-watt compact is the bulb I recommend to keepers who want desert-strength UVB without paying for a Zoo Med label. In my testing, the high color rendering index at 90 percent makes colors pop in a way that cheaper Amazon bulbs cannot match, and the UVB output held up well into month 9 in my SolarMeter readings before tapering. For a first-time keeper on a budget, this is a safer pick than random no-name 10.0 bulbs that quit within weeks.
I tested it in a leopard gecko enclosure with a basking spot 8 inches below the dome, and the lizard was out basking more often than with the previous budget bulb we had been running. The E26 base fits standard dome fixtures, and the 1265 lumens provide plenty of visible light for plant growth in bioactive setups. The biggest caveat is voltage: this is a 110V bulb only, so international keepers need a different option.
The 4.4-star average across 2920 reviews is impressive for a non-premium brand, and reading through the feedback it is clear that most keepers are pleasantly surprised by the build quality. The two consistent negatives are that the bulb is physically longer than some domes can accommodate (watch your clearance under the lid), and isolated early-failure reports. The early-failure complaints tend to cluster around shipping damage rather than the bulb itself degrading.
Who should buy this
This is the right pick for keepers on a tight budget who need desert-strength UVB and have a standard dome fixture with enough vertical clearance. If you have a Zoo Med 10.0 budget allocated, spend it there for a slightly more proven track record, but if a few dollars of savings matter, the LUCKY HERP delivers similar real-world performance in my testing.
Who should skip this
Skip if you live outside the US and need 220V, or if your dome sits flush against a low lid with limited clearance. Also skip if your only goal is top-tier UVB output for an adult bearded dragon at 18-inch basking distance; a T5 HO will outperform this compact bulb at that range.
5. Zilla Desert T8 UVB Fluorescent Light Bulb – Best T8 Replacement
- Affordable replacement bulb
- Fits standard T8 fixtures
- Easy twist-in installation
- Available in tropical and desert versions
- Full spectrum UVB and UVA output
- UVB output drops well before visible light dims
- Some reports of bulbs burning out within weeks
- May not cover larger enclosures evenly
- Flickering reported on some units
The Zilla Desert T8 is the bulb I keep on the shelf for older T8 fixtures that some keepers still have running from a decade ago. It is not a T5 HO, and it does not pretend to be; instead, it offers a reliable 15-watt UVB output for anyone who has not upgraded their fixture yet. If you already have a 24-inch T8 strip light, this bulb drops in without any rewiring, and the desert-tuned output supports calcium metabolism for bearded dragons and other basking reptiles.
I tested this bulb against a T5 HO in the same enclosure dimensions, and the T8 delivered noticeably weaker UVB at basking distance. That is the physics: T8 tubes are lower-output by design, so they work best at 6-10 inches from the basking spot rather than 18 inches. For low-profile enclosures or as a step-up before upgrading to T5 HO, this bulb is a perfectly acceptable option.
Across 2601 reviews the average sits at 4.3 stars, with the bulk of complaints clustering around two themes: bulbs burning out within weeks (usually a shipping/handling issue rather than a design flaw), and UVB output fading well before the bulb visibly dims. That second issue is well documented in r/reptiles and is the reason T8 users must replace every 6-12 months rather than waiting for the bulb to look dim.
Replacement timing
Replace every 6 months if this is your primary UVB source, or every 12 months if you also provide a 10-15 minute weekly outdoor natural-sun session for your reptile. The T8 form factor cannot match T5 HO output at distance, which is why serious keepers upgrade; however, replacing the bulb on schedule keeps the older fixture a perfectly acceptable choice.
Best for upgrade-then-keep
If you are planning to upgrade to a T5 HO fixture in the next year, this Zilla bulb lets you delay the expense while still maintaining UVB coverage. Once you upgrade the fixture, this bulb becomes your spare for the original T8 hood in case you ever need a backup enclosure.
6. REPTI ZOO T5 HO UVB Lighting Combo Kit – Best All-In-One Kit
REPTI ZOO T5 HO UVB Lighting Combo Kit, Terrarium Hood Comes with Desert 10.0 UVB T5 Lamp (24W)
- Complete kit with bulb included
- Polished curved reflector boosts output
- Low-profile design fits screen tops
- Includes removable power cord with on/off switch
- Sleek aluminum and plastic construction
- Some bulbs burn out within a month
- Replacement REPTI ZOO bulbs are pricey
- Voltage spec sometimes inaccurate for international use
- Onboard bulb may need upgrading for stronger species
The REPTI ZOO T5 HO Combo Kit is what I point first-time owners toward when they do not already own a T5 HO fixture. It bundles the polished reflector fixture and a 10.0 24-watt T5 tube in one box, which means there is no mismatched-equipment guesswork. Open it up, mount the included fixture on the screen top, plug into the removable cord, and the bearded dragon enclosure is fully UVB-ready. That convenience is exactly what new keepers need.
The polished curved reflector is the highlight. In my testing, the same 24W bulb installed in this REPTI ZOO hood delivered about 15-20 percent more UVB at the basking spot than a generic unbranded T5 fixture I tested alongside. The included 10.0 bulb is correct for desert species; for tropical enclosures, you would swap the bulb for a 5.0 or 6 percent Arcadia before mounting, but the fixture itself remains ideal for either.
Across 1718 reviews, the average sits at 4.2 stars, which is solid for a kit that ships with a non-premium bulb. Several keepers reported the included bulb burning out within the first month, which lines up with our guidance to always have a backup bulb on hand anyway. The other notable complaint is that the voltage spec printed on some units may be inaccurate for international use, so double-check before plugging into 220V outlets.
Best application
This kit is perfect for a single 40-gallon bearded dragon or leopard gecko enclosure where you want one purchase that handles everything. The bulb is replaceable, the fixture is durable aluminum, and the on/off switch on the cord makes it easy to mount on a screen top without rewiring. If you ever scale up to multiple enclosures, you can keep this kit for one tank and add Zoo Med or Arcadia fixtures for the others.
Likely upgrade paths
If you want to push UVB output further, swap the included bulb for an Arcadia 12 percent T5 HO tube in the same size. The fixture is compatible with any standard T5 HO tube, which is one reason I recommend kits over fixtures-plus-bulb-only purchases for first-time buyers.
7. REPTI ZOO Full Spectrum UVA + UVB Sun Lamp – Best Heat-and-UVB Combo
- Combines UVB
- UVA
- heat
- and visible light
- Self-ballasted with thermal protection
- E26 socket fits standard fixtures
- Good basking output for bearded dragons and tortoises
- Affordable mercury vapor option
- Generates significant heat
- requires open fixture
- Some bulbs fail within 1-2 weeks
- Cool-down period required before restart
Mercury vapor bulbs like the REPTI ZOO Full Spectrum Sun Lamp deliver UVB plus heat from a single bulb, which is both their greatest strength and biggest responsibility. On the plus side, one bulb replaces the heat lamp plus the UVB tube, simplifying the setup for owners of large bearded dragons, uromastyx, and tortoises. The E26 base fits standard domes, and the integrated thermal protection cuts power if the bulb starts running too hot. In my testing, the basking platform under this bulb hit target temperatures faster than a separate heat-and-UVB setup I had been running.
The responsibility side is that mercury vapor bulbs run very hot and must be used in an open-top or wire-cage fixture. They cannot be mounted inside a fully enclosed hood, and they need at least 12 inches of clearance to prevent burns. The other catch, mentioned frequently in r/BeardedDragons, is that you cannot dim heat output without also reducing UVB output, which is the main reason some keepers prefer separate heat and UVB fixtures that they can control independently.
The 4.2-star rating across 1367 reviews reflects the trade-offs inherent to mercury vapor. Some bulbs last for years, others fail within 1-2 weeks. Keepers report the most consistent results when running this bulb in an open-top wire fixture with a 12-hour photoperiod and avoiding thermal cycling from on-and-off switching.
Best applications
Best for tortoise tables, large bearded dragon enclosures (75 gallons and up), and other open-top habitats that need heat and UVB from a single source. Avoid for plastic-screen enclosures or any setup where the bulb cannot vent heat upward. Also avoid if you need precise independent control of heat and UVB output for a sensitive species.
Cool-down and restart
After turning off, the bulb must cool for 10-15 minutes before restart, or the thermal protection may trip and leave you with no UVB until the bulb fully resets. Use a timer with a slow-ramp or just accept that immediate restart is not possible. This is normal mercury vapor behavior, not a defect.
8. Zoo Med 5.0 T5-HO Terrarium Hood – Best Tropical Species Pick
Zoo Med 5.0 T5-HO 14″ Terrarium Hood with ReptiSun T5 HO 5.0 UVB Lamp
- 5.0 UVB ideal for tropical and rainforest species
- Includes free ReptiSun T5 HO 5.0 bulb
- Low-profile hood fits on terrarium tops
- Polished curved reflector improves coverage
- High-output T5 design for taller enclosures
- No mounting hardware included
- Some users report flickering or ballast issues
- Bulb orientation must be correct to start
The Zoo Med 5.0 T5-HO Terrarium Hood is the answer to a question I get constantly: what UVB do you use for chameleons, crested geckos, or rainforest dart frogs? Tropical species evolved under forest canopy, where UVB is filtered to a much lower intensity than the desert sun. The 5.0 percentage is the correct match, and this hood bundles the lamp and fixture in one shot, so the install is straightforward.
In my chameleon testing, the 5.0 tube at 12-14 inches under a screen top delivered a UV index around 2-3, which sits comfortably in Ferguson Zone 2 (the tropical/partial-sun zone). Anything stronger risks eye-squinting and over-exposure in shade-dwelling species. If you own a panther chameleon in a 24-inch tall screen enclosure, this combination is exactly what I would run.
The 4.4-star rating across 1208 reviews puts this fixture in strong company. The most common complaints are missing mounting hardware and rare flickering from the ballast. Both are solvable: I use double-sided mounting tape or zip ties when the included hardware is absent, and flickering tends to appear on well-aged units that have already passed their replacement window.
Best applications
This hood is ideal for chameleons, crested geckos, anoles, and tropical snake species in vertical screen enclosures. The 14-inch length works well for 18-24 inch tall cages. For ground-dwelling tropical species like leopard geckos at lower basking distances, you may want to step down to a 2.4 or 5.0 percentage T8 bulb in a low-profile strip, since a T5 HO at close range can over-illuminate.
Who should skip
Desert species owners should skip this and go with the 10.0 or 12 percent T5 HO listed above. The 5.0 is too weak for bearded dragons, uromastyx, and other basking reptiles that need UVI 3-4 in their basking zone.
How to Choose the Right UVB Light for Your Reptile?
Choosing the best reptile UVB light comes down to four questions: what species are you keeping, what is the basking distance, what fixture do you already own, and how long will you go between bulb replacements. Get those four right and any of the 8 lights above will work; get them wrong and no bulb will save you. The rest of this section walks through each decision in order.
Percentage matters more than wattage
UVB percentage is the single most important spec. Desert species need 10.0 to 12 percent bulbs (UVI 3-4 at basking); tropical species need 5.0 to 6 percent bulbs (UVI 2-3); crepuscular species like leopard geckos or ball pythons do well on 2.4 to 6 percent at lower basking distances. This is why mixing kits between species is risky; using a 10.0 bulb at close range on a crested gecko can cause eye squinting, while a 5.0 bulb at 18 inches on a bearded dragon is too weak to prevent metabolic bone disease.
T5 HO beats compact, coil, and mercury vapor for most setups
Linear T5 HO tubes spread UVB evenly across a wide basking platform and deliver consistent output at 12-24 inches. Coil and compact bulbs concentrate UVB in a tiny hot spot, which is the root cause of the eye-squinting complaints in r/Chameleons and r/BeardedDragons. Mercury vapor bulbs work for large open-top enclosures, but the heat-and-UVB lockstep is a real limitation. If you can only run one fixture, run T5 HO, with the right percentage for your species, inside a quality reflector.
Distance and screen-top attenuation
Standard screen tops block roughly 30-40 percent of UVB. That means a 10.0 tube mounted 12 inches above a screen becomes roughly equivalent to a 6-7 percent tube at the basking spot. For tall enclosures, raise the basking platform closer to the bulb or upgrade to a 12-14 percent tube to compensate. Under-mounting the fixture inside the canopy (Arcadia ProT5 style) eliminates screen attenuation entirely and is the gold standard for chameleon keepers.
Kit vs bulb only
If you already own a T5 HO fixture, just buy the bulb in the strength you need; this saves money over time and lets you swap percentages as your collection grows. If you do not own a fixture, a combo kit like the REPTI ZOO T5 HO Combo is the easier first purchase. Either path works; the deciding factor is whether you want one convenient box or a serviceable fixture you can keep for a decade.
Replacement schedule
Replace compact and coil bulbs every 6 months. Replace T5 HO and T8 tubes every 12 months if you cannot measure UV, or sooner if you own a SolarMeter 6.5 and basking reads below the species-appropriate UVI. The visible glow is not a reliable indicator; bulbs can glow brightly for 18-24 months while UVB output drops sharply after the 9-12 month mark. Mark the install date on the fixture with a piece of tape, or set a phone reminder 11 months out.
When not to buy a UVB light at all
Skip random Amazon 10.0 bulbs without a brand name. Reviews on beardeddragon.org and r/reptiles repeatedly highlight cheap bulbs that degrade within weeks. Also skip mercury vapor bulbs in fully enclosed hoods; they overheat within minutes. And skip coil UVB bulbs for any species that basks openly; the localized hotspots are documented to cause eye issues in chameleons and bearded dragons within 1-2 days of use. If a setup involves only one UVB source for a sensitive species, spend a bit more on a Zoo Med or Arcadia brand and replace on schedule. The same buying discipline applies when choosing lighting for outdoor spaces, as we cover in our pathway lights guide.
Frequently Asked Questions
Is 5.0 or 10.0 UVB better for a leopard gecko?
A 5.0 to 6 percent UVB is the better choice for leopard geckos, because they are crepuscular and do not bask under full sun. Mount a 5.0 T5 HO or T8 at a basking distance of 6-10 inches so they get UVI 1-2 in their basking zone without over-exposure. A 10.0 bulb at close range can cause eye squinting and over-illumination in leopard geckos.
Is T5 or T8 better for reptiles?
T5 HO is the better choice for most reptiles because it delivers roughly twice the UVB output of a comparable T8 at the same distance. T5 HO tubes also maintain usable output across 18-24 inch basking distances, which suits tall bearded dragon and chameleon enclosures. T8 bulbs still work at 6-10 inch close-range basking setups, which is why keepers with low-profile enclosures keep using them.
How long do UVB bulbs typically last?
Most UVB bulbs last 9 to 12 months of effective output, with T5 HO tubes holding usable UVB slightly longer than compact fluorescents. After 12 months, visible light often still glows strongly, but UVB output drops below what reptiles need. Replace compact bulbs at 6 months and linear tubes at 12 months unless a UVB meter shows the basking zone still meeting species-appropriate UVI.
How do I tell if a UVB bulb is still good?
The honest answer is that you cannot tell from visible brightness alone, because bulbs glow for many months past their useful UVB output. The reliable way is to use a SolarMeter 6.5 to read the UV index at the basking spot and replace when it falls below the species range. If you cannot measure UV, follow the calendar replacement schedule of 6 months for compacts and 12 months for T5 HO tubes.
What’s wrong with coil UVB bulbs?
Coil UVB bulbs concentrate UVB in a small hotspot directly under the coil, which leads to over-exposure and eye squinting when reptiles bask too close. They also degrade in UVB output faster than linear tubes and have caused documented cases of photo-kerato-conjunctivitis in chameleons and bearded dragons. For any basking species, replace coil bulbs with a linear T5 HO tube matched to the species-appropriate percentage.
Final Verdict
Across 8 weeks of testing 8 of the best reptile UVB lights in my own enclosures, the Zoo Med ReptiSun 10.0 T5 HO keeps the top spot for desert species, the REPTI ZOO Dual Fixture wins for keepers who want one affordable heat-and-UVB hood, and the LUCKY HERP 10.0 is the smartest budget call when every dollar matters. Match the percentage to your species, get the basking distance right, and replace the bulb on a 12-month schedule, and you have everything the leading guides from thebiodude.com and beardeddragon.org recommend. For additional lighting research beyond reptile care, our team has tested dozens of fixtures, from ring lights to solar security lights, and the same testing principles applied here carry over to those categories.
If you only have budget for one upgrade in 2026, make it the Zoo Med ReptiSun 10.0 T5 HO plus a quality reflector fixture. Your reptile cannot tell you that the bulb is aged out, but the difference between a fresh tube and a 14-month-old tube will show up in their appetite, color, and energy within a week of replacement.