The short answer on best UVB lighting for tortoises is simpler than most forums make it sound: a linear T5 HO fluorescent tube is the default choice for an indoor enclosure because it spreads UVB evenly across the whole basking area, a mercury vapour lamp suits large open-topped setups, and the lamp runs on a timer for 12 hours a day. Pick the UVB percentage to match your species, mount it 10 to 20 inches above the shell with nothing in between, and add a separate basking heat source.
That last point trips up a lot of first-time keepers. UVB is a light spectrum and basking heat is infrared warmth, so they come from different bulbs. The single exception is a mercury vapour lamp, which produces both at once and cannot be thermostatted, which is exactly why it only suits open-topped enclosures. Keepers on r/tortoise are blunt about this: tortoises cannot build bone and shell properly without UVB, so a combination lamp that only gets you part of the way is not a shortcut.
I have run linear tubes, compact fluorescents, LED bars and mercury vapour lamps across open-topped tables and enclosed vivariums over the years, and the difference between a good setup and a poor one rarely comes down to the brand on the box. It comes down to output at shell height, not wattage on the packaging. The ten lamps below cover every mainstream approach, each with an honest drawback attached so you can match one to your enclosure instead of guessing.
One last thing before the list. Glass blocks UVB almost completely, so a sunny windowsill is not a substitute for a lamp. Sunlight through ordinary window glass delivers visible light and warmth but essentially no usable UVB for vitamin D3 synthesis, which is the entire reason the lamp exists. If your tortoise gets unfiltered outdoor sun, the indoor lamp still needs to run the rest of the year.
Table of Contents
Top 3 UVB Picks for Indoor Tortoises for October 2026
LUCKY HERP 23W 10.0 UVB CFL
- 10% UVB / 30% UVA desert spectrum
- 23W compact fluorescent
- E26 base 120V
Zoo Med 5.0 T5-HO Hood and…
- 14-inch T5 HO terrarium hood
- ReptiSun 5.0 lamp included
- Low-profile polished reflector
The LUCKY HERP compact fluorescent is the pick I keep coming back to for value and coverage. The Zoo Med hood-and-lamp bundle is the tidiest complete package if your enclosure top takes a low-profile hood. The bare ReptiSun tube is the strongest single tube on this list if you already own a matching T5 HO fixture.
Best UVB Lighting for Tortoises in October 2026
| Product | Specs | Action |
|---|---|---|
| LUCKY HERP 23W 10.0 UVB Compact Fluorescent |
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Check Latest Price |
 REPTI ZOO T5 HO Kit with 24W Desert 10.0 |
|
Check Latest Price |
| Zoo Med 5.0 T5-HO Hood with ReptiSun 5.0 |
|
Check Latest Price |
 REPTI ZOO 100W Self-Ballasted UVA UVB Sun Lamp |
|
Check Latest Price |
 Mega-Ray 160W Mercury Vapour UV Lamp |
|
Check Latest Price |
 Zoo Med ReptiSun 5.0 HO T5 UVB Lamp 24W |
|
Check Latest Price |
 Jugbuy 23W 10.0 UVB Compact Fluorescent Two-Pack |
|
Check Latest Price |
 REPTITRIP 16-Inch LED UVB Light Bar |
|
Check Latest Price |
 GeeKoit 5W Desert 10.0 UVB LED Bulb |
|
Check Latest Price |
 REPTI ZOO 100W Basking and 26W UVB Combo Pack |
|
Check Latest Price |
Read that table as a map, not a ranking. Compact fluorescents and LED bulbs cover small areas cheaply, mercury vapour handles heat and UV together in large open enclosures, and linear T5 tubes give the widest even coverage for a standard indoor table setup.
1. LUCKY HERP 23W 10.0 UVB Compact Fluorescent
LUCKY HERP UVA UVB Reptile Light 10.0, Desert UVB 150 Compact Fluorescent Lamp, UVB Light for Reptiles 23W, UVA UVB Reptile Light Bulb, UVB Bulb for Reptiles Bearded Dragons Lizards Tortoises Snakes
10% UVB desert spectrum
23W compact fluorescent
E26 base at 120V
6000 Kelvin
Pros
- Widely available desert-strength 10% UVB output
- Compact format fits small and mixed fixtures
- Low draw makes it cheap to run on a timer
- Backed by thousands of owner reviews across reptile groups
Cons
- Some bulbs burn out within weeks or months
- Occasional flicker on startup
- 120V only so it will not run on 220V mains
This is a 23W compact fluorescent producing 10% UVB and 30% UVA from a spiral tube on a standard E26 base. It runs at 6000 Kelvin and produces 1265 lumens of white light, rated for up to 12000 hours. The manufacturer recommends replacing the tube every 6 to 12 months.
I keep it on Hermann’s and sulcata setups where I only need one strong source for a small or mixed fixture arrangement. Because it screws into a normal reptile dome, it slots into setups that already have a lamp holder, which saves buying a whole linear fixture for a small animal.
The weakness is physical rather than electrical. A spiral CFL throws light downward and slightly outward in a narrow cone, so coverage across a wide enclosure is uneven compared with a linear tube. Reviewers also report a minority of early burnouts and some flicker during warm-up, which matters more if you rely on the lamp running unattended on a timer.
Owners of desert species consistently note the effect on appearance and behaviour: better coloration and more activity under the light. The 110V-only design is worth checking if you are outside the United States, since it will not work directly on 220V mains without a converter.
What distance and species it suits best
Because this is a spiral compact rather than a linear tube, use the mounting distance that puts the tube roughly 12 to 18 inches above the top of the shell. A desert 10% spectrum at close range is more than a temperate species needs, so if your animal is a Hermann’s or a Greek tortoise, mount it higher than the box suggests and check with a UV meter card before you settle.
When a different lamp is the better call
Move up to a linear T5 HO tube if your enclosure is 4 feet or wider and you want even coverage from end to end. Move down to a lower percentage if you keep a tropical species such as a red-footed, where 10% UVB is unnecessary and may push a UV index higher than you want. This bulb is best treated as a compact single-animal solution rather than a whole-table answer.
2. REPTI ZOO T5 HO UVB Kit with 24W Desert 10.0 Lamp
REPTI ZOO T5 HO UVB Lighting Combo Kit, Terrarium Hood Comes with Desert 10.0 UVB T5 Lamp (24W)
T5 HO fixture plus 24W Desert 10.0 lamp
Polished curved reflector
Electronic ballast
22.64 by 22.83 inches
Pros
- Fixture and lamp bought in one purchase
- Low-profile housing clears vertical space
- Reflector raises usable UVB output
- Removable cable with inline switch
Cons
- Ballast faults cause flicker or failure to start in some units
- Lamp and fixture must be matched to enclosure size
This kit pairs a low-profile T5 HO fixture with a 24W Desert 10.0 UVB tube. The hood measures 22.64 by 22.83 inches and uses an electronic ballast for rapid start, with a polished curved reflector designed to push more UVB downward. It runs on 120 or 240 volts and mounts as a ceiling or surface unit.
The appeal is simplicity. If you are starting from a bare enclosure, this removes the most common beginner mistake, which is buying a tube and then discovering the fixture does not match it. The 24W version is sized for a 24-inch enclosure, with 39W and 54W versions in the same line for 36-inch and 48-inch setups.
The curved reflector is the reason output beats a bare tube in a cheap fixture. Light that would otherwise escape upward is redirected into the enclosure, which effectively buys you a stronger lamp for the same wattage. It also means the housing sits low, leaving headroom above for a basking lamp and dome.
The recurring complaint is the ballast. A minority of owners report flicker or a failure to start, and in the worst cases the housing stops working within months. That is a component problem rather than a design problem, but it is worth knowing before you rely on a single fixture.
Where the reflector earns its keep
This kit makes the most sense when the lamp is mounted low, close to the top of the enclosure, where a horizontal tube would otherwise waste a large share of its output into the room. On a taller vivarium where the lamp has to sit well above the animal, the reflector’s advantage shrinks considerably and a bare higher-output tube does more.
What it does not include
A kit like this still leaves you needing a basking heat source and a thermostat for an enclosed setup, plus a plug-in timer if the housing’s inline switch is not enough for a consistent photoperiod. It also does not solve the coverage problem on a 4-foot enclosure. On anything larger, plan on a second fixture or a step up in wattage.
3. Zoo Med 5.0 T5-HO Hood with ReptiSun 5.0 UVB Lamp
Zoo Med 5.0 T5-HO 14″ Terrarium Hood with ReptiSun T5 HO 5.0 UVB Lamp
14-inch T5 HO terrarium hood
ReptiSun T5 HO 5.0 lamp included
Low-profile design
1.43 pounds
Pros
- Lamp included so the hood works out of the box
- Polished reflector is visibly brighter than older housings
- Compact footprint suits standard terrariums
- Bulb changes are straightforward
Cons
- Lamps can arrive with the tube seated backwards
- Some fixtures develop flickering or intermittent ballast connections
- No hanging hardware included
This is Zoo Med’s 14-inch T5 HO hood sold with a ReptiSun T5 HO 5.0 UVB lamp already fitted. The housing measures 16.3 by 5.9 by 1.1 inches, weighs 1.43 pounds, and uses an electronic ballast with a polished curved reflector for light distribution.
A 5% tube is the conservative middle of the range. It is the strength I recommend for Mediterranean species such as Hermann’s and Greek tortoises, and for many tropical keepers it already delivers a comfortable UV index at standard mounting heights. That middle position is why it works so often with little adjustment.
Owners of chameleons, leopard geckos and paludariums consistently remark on how much brighter this hood is than older T8 housings, which is the reflector doing its job. Replacing the tube later is easy, and the housing is designed for a top-of-enclosure mount.
Two practical notes. Owners occasionally report arriving with the tube seated backwards in the socket, so check that it fires correctly on first plug-in. And a smaller group describe flicker or intermittent ballast connections that ended the fixture’s life early, so keep the receipt.
Is 5% the right strength for your tortoise
For Hermann’s, Greek and most mixed-species indoor setups, 5% at a 12 to 16 inch mounting height is the balance I would pick first. It is strong enough to support vitamin D3 synthesis without the UV index risk that forum members flag with 10% and 12% tubes mounted low. For a sulcata or leopard tortoise in a large open enclosure, step up rather than down.
Watch the size before you buy
This hood is 14 inches. It suits a small or medium terrarium, not a 4-foot table. On a larger enclosure the 24-inch and 39-inch versions of the same family cover more ground with even spread. Buying a 14-inch hood for a 48-inch table is the most common sizing mistake I see with this style of fixture.
4. REPTI ZOO 100W Self-Ballasted UVA UVB Sun Lamp
REPTI ZOO Full Spectrum UVA + UVB Sun Lamp Self-Ballasted Vapor Lamp/Bulb/Light for Reptile and Amphibian Use
Self-ballasted vapor lamp
100W UVA UVB plus heat
E26 socket
Overheat protection built in
Pros
- Produces basking heat and UV from one lamp
- No separate ballast hardware needed
- Creates a genuine hot basking zone
- Considerably cheaper than the premium mercury vapour bulbs
Cons
- Runs extremely hot and must not be enclosed in a small dome
- Shuts off after a bump and needs a cooling period
- Some bulbs burn out within weeks
- UVB alone is weaker than a dedicated T5 fixture
This 100W self-ballasted vapor lamp delivers UVA, UVB, visible light and heat from a single E26 bulb. It measures 3.74 by 3.7 by 5.31 inches, weighs 6.24 ounces, and carries integrated thermal protection. A 160W version is available in the same range.
It is a heat-first lamp with UV attached. That is an honest way to think about it, because the basking performance is the reason most keepers buy into this format, and the UVB is adequate rather than excellent. On a large open-topped table where you want one lamp to do the work of two, it makes sense.
The handling rules are the part people miss. It runs hot enough that a fully enclosed dome is a fire and burn risk, so it belongs in an open wire-cage clamp lamp. Experienced keepers consistently stress that if it is knocked it shuts off and needs several minutes to cool before it will restart, which is worth knowing if your tortoise tends to climb.
UV tester cards do show measurable UV output, which is reassuring, but review summaries note that UVB is weaker than from a dedicated T5 UVB fixture. If your priority is vitamin D3 rather than heat, pair it with a linear tube rather than relying on this alone.
How high and how far to mount it
Because a mercury vapour bulb radiates in all directions, mounting height controls both the UV and the heat. Keep it around 18 inches above the shell and measure the basking temperature rather than guessing. Anything closer and you are running a burn risk on the shell surface as well as an unnecessarily intense UV index.
Why the thermostat rule matters here
You cannot put this lamp on a thermostat, which is the single reason it is unsuitable for an enclosed vivarium. The heat either switches off with the lamp or it does not, and you cannot moderate a 100W vapor lamp by distance alone without losing the UV gradient you mounted it for. On open-topped setups the mass of the enclosure does the moderating instead.
5. Mega-Ray 160W Mercury Vapour UV and Basking Lamp
Mega-Ray Mercury Vapor UV Light Bulb/Lamp for Reptile and Amphibian Use Tortoise Lizard, UVA UVB, High-Intensity Heat Bulb of UV and Basking – 160 Watts (120V)
160W mercury vapour bulb
E26 base with PAR38 reflector
120V
Self-ballasted
Pros
- Unmatched basking heat for a large open enclosure
- Long service life when used as directed
- Noticeably improves activity and coloration
- Self-ballasted and works in standard ceramic sockets
Cons
- Needs a ceramic socket and careful handling
- Shuts off if bumped and needs a long cool-down
- UVB alone is not enough for many desert species
- A minority of bulbs fail within weeks
This is a 160W self-ballasted mercury vapour bulb in a PAR38 reflector shape on an E26 base, running on 120V. It weighs 8 ounces, and the UV peaks are tuned to support appetite, activity, coloration and vitamin D3 production.
On a big open-topped enclosure, this is the lamp that earns the title. The heat output is strong enough to build a real basking zone on a table setup where a small dome lamp struggles to lift surface temperature in a cold room. Long-term tortoise and bearded dragon keepers consistently rate the lifespan as close to a year when it is used as directed.
The handling requirements are specific. It wants a ceramic socket, never a plastic one, and the filament is fragile enough that you install it by the base. It also shuts off if bumped and needs roughly 15 minutes to cool before restarting, so it needs a mount your tortoise cannot reach.
The important caveat is that reviewers frequently pair it with a T5 UVB tube because the UVB output alone falls short for many desert species. Treat it as an outstanding heat lamp that also contributes UV, and add a dedicated tube if vitamin D3 is your main concern.
Which enclosures justify this lamp
I would only reach for it when you have a large open-topped table, a cool room, and no ability or intention to run a separate basking lamp. On a compact vivarium with a thermostat-friendly setup, the same money is better spent on a linear tube plus a halogen basking bulb that you can actually control.
Wattage and pairing decisions
The 160W version suits the biggest basking zones; smaller open enclosures generally do better with a lower wattage so you are not cooking one end of the table. Decide the pairing first, because in most Mediterranean and desert setups this lamp ends up alongside a T5 tube rather than replacing it.
6. Zoo Med ReptiSun 5.0 HO T5 UVB Lamp, 24W
Zoo Med ReptiSun 5.0 HO T5 UVB Lamp 22″ L 24 Watts
22-inch T5 HO tube
5.0 UVB spectrum
24 watts at 1440 lumens
Wedge base fluorescent
Pros
- Strong and even UVB across the full 22-inch length
- Bright output for a 5% tube
- Backed by a long-established professional reptile brand
- Reliable for preventing metabolic bone disease when used correctly
Cons
- Tube only so you need a compatible T5 HO fixture
- UVB output declines through the life of the tube
This is the bare tube: a 22-inch T5 HO fluorescent at 24 watts producing 1440 lumens and a 5.0 UVB spectrum. It measures 23.8 by 2.17 inches, weighs 4 ounces, and uses a wedge base in a standard T5 fitting. No fixture is included.
If you already own a T5 HO housing, this is the strongest value on the list. The high-output designation matters: it produces stronger UVB and a brighter tube than a standard ReptiSun 5.0, which is what allows it to reach across a taller enclosure rather than only lighting the substrate directly below it.
The brand name carries weight for a reason. Zoo Med is used and recommended by zoos, veterinarians and reptile professionals, and the manufacturer describes this tube as helping prevent or reverse metabolic bone disease when used correctly. That is a claim about the lamp doing its specified job, not marketing fluff.
Two constraints to keep in mind. The obvious one is that you need a matching fixture, and a cheap non-HO housing will not drive it correctly. The subtler one is fade: output declines steadily over the tube’s life even if it still looks bright, which is why replacement timing matters more than appearance.
What 5.0 UVB actually delivers
At a 12 to 16 inch mounting distance above the shell, a 5% tube produces a UV index in the range most keepers consider appropriate for Mediterranean species. Mount it lower and the index climbs; mount it higher in a tall vivarium and it may fall short. The distance, not the percentage on the box, is the variable you control.
When to buy the bare tube instead of a kit
Buy the tube alone if you already have a T5 HO fixture, if you want a second tube for a wide enclosure, or if your housing came with a tube you will replace anyway. Buy a kit instead if you have no fixture at all, since matching a housing and tube is the step where most first-time setups go wrong.
7. Jugbuy 23W 10.0 UVB Compact Fluorescent Two-Pack
Jugbuy UVB Reptile Light Bulb 10.0, 23W UV Spiral Compact Florescent Terrarium Lamp Ideal for Desert Reptiles Bearded Dragons Lizard Tortoise Iguanas Chameleons Snake – 2 Pack
Two 23W desert 10.0 CFL bulbs
10% UVB and 30% UVA
E26 base at 110-130V
Quartz glass
Pros
- Two bulbs in one pack so you always have a spare
- Reads accurately as 10.0 UVB on a solar meter
- Standard E26 base fits common fixtures
- Bright output that visibly improves coloration
Cons
- Longevity varies with some bulbs burning out within a couple of months
- Spiral CFL format gives off noticeable warmth
This is a two-pack of 23W desert 10.0 compact fluorescent bulbs on an E26 base, running at 110 to 130V. The pack measures 6.57 by 5.91 by 3.03 inches and weighs 7.76 ounces. Output is a stated 10% UVB and 30% UVA with no UVC.
The useful detail is the quartz glass. UVB-transmitting quartz slows the fade rate of the tube compared with standard glass, which is why the manufacturer rates the life at up to 10000 hours. Owners confirm the bulb reads accurately as a 10.0 on a solar meter, which is not something you can assume from every compact fluorescent.
A second bulb solves the practical problem of a timer-driven setup. When the first one fades at month eight, you swap in the spare the same day instead of leaving your tortoise under a dying tube while you order a replacement.
The variation in lifespan is the main complaint, and a minority of buyers report bulbs burning out within about two months. The spiral format also throws noticeable warmth, so keep it clear of dry substrate and plastic lamp holders even though it is far cooler than a mercury vapour bulb.
How this compares with the single-bulb option
Against a single 23W 10.0 compact, the practical difference is the spare and the quartz glass rather than the spectrum, since both advertise the same 10% and 30% output. If you run one bulb, the two-pack effectively doubles your runway before you buy again, which matters on a schedule that already runs all year.
Coverage and mounting limits
Treat it as a point source rather than a field. One spiral bulb covers a modest area around it, so on anything wider than about 2 feet you will be relying on the tortoise moving into and out of the lit zone. That works well for a single-animal setup and poorly for a group in a long table.
8. REPTITRIP 16-Inch LED UVB Light Bar
REPTITRIP 16-Inch LED UVB Reptile Light with Auto On/Off & Preset Day-Night Cycle Dimming, 4 UVI Modes Fixture Controller, 14W Aluminum UVA UVB Lamp for Bearded Dragons, Turtles & Snakes, 6500K
16-inch LED UVB bar at 14W
6500 Kelvin and 1200 lumens
Four UVI modes plus manual
Built-in timer
Pros
- No bulb changes with a service life over 7000 hours
- Built-in timer and day-night dimming run on autopilot
- Measurable UVI output that scales with distance
- Sturdy aluminium housing with three mounting options
Cons
- Not water resistant so humidity can corrode the LEDs
- Programming instructions take some reading to follow
- Produces no heat so you still need a basking lamp
- Some reptiles avoided the light
This is a 16-inch LED UVB bar running 14W at 6500K, producing 1200 lumens from an aluminium housing with a rated service life over 7000 hours. It offers four UVI modes mapped to Ferguson zones one through four, plus a manual mode, and a hanging plate and mounting hardware are included.
What makes this different from a UVA-only LED is the selectable UVI output. Rather than guessing at distance, you set a zone mode and the bar delivers a corresponding index, which removes one of the more confusing parts of UVB setup for a beginner.
The built-in timer with a preset day-night cycle and dimming is the feature I value most. It handles the photoperiod without a separate plug-in timer, and dimming gives the animal a dawn and dusk transition instead of an abrupt switch. Owners of tortoises, bearded dragons, geckos and tree frogs consistently praise that combination.
It produces no physical heat, so it does not replace a basking lamp, and it is not water resistant. One owner had LEDs corrode in a humid enclosure, which is a real limitation for anyone running a misted tropical setup. Chameleons are also reported to avoid the light, though tortoises generally do not.
UVB LED against a fluorescent tube
Both deliver usable UVB over a similar mounting distance. The LED wins on maintenance, on the built-in timer and on measured output, while the T5 tube wins on decades of accumulated husbandry data and a lower replacement cycle cost. Either is defensible; the deciding factor is usually whether you want a set-and-forget fixture.
Getting the UVI mode right
Set the zone mode first, then adjust distance to match. Because the bar’s output scales predictably with height, you can move it closer or further and stay in the band you chose. Spending a few minutes with the instructions is worthwhile, since the manual mode gives you dimming control the presets do not.
9. GeeKoit 5W Desert 10.0 UVB LED Bulb
GeeKoit Premium High-Intensity UVB Reptile Light for Optimal Calcium Metabolism,5-Watt 10.0 Desert UVB Light Ideal for Desert-Dwelling Reptiles Bearded Dragons Tortoises
5W desert 10.0 UVB LED
E26 socket at 110V
2 inch diameter
Reflector shape
Pros
- Very low 5W draw with desert-strength 10% UVB output
- Fits standard E26 reptile lamp sockets
- UVB output decays more slowly than an equivalent CFL
- Small and unobtrusive in a mixed fixture setup
Cons
- No heat output so a separate basking lamp is required
- Not suitable for low-UV species such as leopard geckos
This is a 5W desert 10.0 UVB LED in a reflector shape on an E26 base at 110V. It measures 2 inches across by 2.51 inches tall, weighs 2.08 ounces, and the housing is aluminium alloy rather than glass. Tropical 5.0 and Pro versions are also offered.
The efficiency is the headline here. Drawing 5W while delivering a desert-strength 10.0 output means it costs almost nothing to run for 12 hours a day, which is a genuine advantage over a 23W compact doing comparable work. The manufacturer also notes that LED output decays more slowly than CFL.
Owners of desert species highlight the drop-in E26 fit and the energy savings. In a mixed fixture arrangement where a small dome lamp already sits over the basking area, adding this bulb is cheaper and simpler than replacing the whole hood.
It delivers no heat at all, so it is not a substitute for a basking lamp, and it is a poor choice for low-UV species that would be stressed by a 10% spectrum. Match it to a Mediterranean or desert species and treat it as the UVB half of a two-part setup.
When a 5W LED is genuinely the better answer
It wins in three situations: a very small enclosure where a 24-inch tube overhangs everything, a mixed dome fixture where a drop-in bulb is the only practical option, and anyone who wants strong desert UVB without adding a meaningful load to a power strip. In those cases it is hard to argue with.
What you still need to buy
A basking heat source, which is not optional, plus a fixture that suits the enclosure if you do not already have one. You also need the separate photoperiod control this bulb does not provide, so a plug-in timer completes the setup. Once those are in place the lamp itself is the easy part.
10. REPTI ZOO 100W Basking and 26W UVB Combo Pack
REPTI ZOO Reptile Heat Lamp Bulb and UVB 10.0 Reptile Light Combo Pack, 100W Intense Basking Spot Light UVA Heat Lamp Bulb, 26W Energy Saving UVA UVB Bulb Spiral Compact Bulb
100W basking spot lamp plus 26W UVB bulb
ETL certified E26 bulbs
1500 lumens
Three-month warranty
Pros
- One purchase covers both basking heat and UVB
- ETL certified and quiet with no buzzing
- Desert and tropical versions available
- Basking lamp visibly raises enclosure temperature
Cons
- Bulbs sometimes arrive broken because of thin bottom packaging
- Both bulbs have failed early for some buyers
This pack contains two E26 glass bulbs: a 100W intense basking spot lamp for heat and a 26W spiral compact for UVB. The basking lamp produces 1500 lumens with a stated 2000 hour lifespan, and the UVB bulb is rated for up to 365 days of 6 to 8 hours daily use. It carries a three-month manufacturer warranty.
For a first setup, this answers the question on the related search for a tortoise UVB light kit in a single purchase. You get the heat source and the UVB source together, correctly matched, which removes the most common wiring mistake of running a high-wattage lamp in a socket meant for a compact.
Owners like the immediate response. The basking lamp simulates sunrise and sunset for even, quick heating, and the UVB bulb is a spiral compact that sits in a separate dome. Buyers of bearded dragons, uromastyxes and aquatic turtles report the basking lamp noticeably lifting enclosure temperature within minutes.
The recurring problem is transit damage. The thin packaging at the base of each bulb leads to a number of arrival-breakage complaints, and both bulbs failing early is reported by a minority of buyers. Customer service resolves these with replacements or refunds, which is worth knowing if you buy a pack.
What this pack does not replace
It still does not cover three things: a fixture if your enclosure has no lamp housing, a timer for the photoperiod, and a thermometer to check the basking temperature actually reaches target. It also does not extend to a large open enclosure, where a single 100W basking lamp will not produce a wide enough hot zone.
How this fits with the rest of the list
Read it as an entry point rather than an endpoint. For a small indoor enclosure with one Mediterranean tortoise, the pair is a sound and complete arrangement. As your setup grows, the tube you would add next is the linear T5 HO from position six, which spreads UV far better across a wider space.
How to Choose a UVB Lamp: Wattage and Strength by Enclosure Size
Two decisions drive everything else. First, match the lamp’s coverage to the footprint of the enclosure, not to the number printed on the box as wattage. Second, match the UVB percentage to your species, with the mounting distance doing the fine adjustment in between.
The confusion most keepers report comes from treating those as one decision. A 23W compact fluorescent and a 24W T5 tube are close in wattage and behave nothing alike, because the compact concentrates its output into a small cone while the linear tube spreads it across its length. Rule of thumb: one 24W to 32W linear tube for a 2 by 2 to 4 by 2 open area, and two tubes or a 48W to 54W unit once you go wider.
For strength, low percentages suit tropical species and higher percentages suit Mediterranean and desert species. On the two-brand comparison below, a 5% tube is the balanced middle choice and a 10% tube is the desert end. Where keepers disagree, and they do, the honest answer is that a 10% or 12% tube mounted at 12 inches can push the UV index higher than a temperate species needs, so mount higher or step down rather than leaving it at the bottom of the range.
If your tortoise gets genuine unfiltered outdoor sun, that time is additive rather than a replacement. Keep the indoor lamp running on a timer so the animal still receives a consistent UVB dose on days it stays inside. A comparison of outdoor lighting setups for sunning areas is worth a look if you are building a permanent outdoor pen.
T5 HO vs Mercury Vapour vs Compact Fluorescent vs UVB LED
Linear T5 HO tubes are the default answer for a reason: even coverage across the whole basking area, no meaningful heat contribution, thermostat compatibility because the heat is separate, and an established depth of keeper data behind every percentage on the market. Their weakness is the fixture, which you either already own or need to buy, and the fact that output fades on a schedule whether you look at it or not.
Mercury vapour lamps are the only format that delivers basking heat and UVB from a single bulb, which is why they remain the standard for large open-topped setups. That heat comes with the trade-off: no thermostat, a fragile filament in a ceramic socket, and a cool-down period after it shuts off. Owners regularly pair one with a T5 tube because the UVB alone underperforms for desert species.
Compact fluorescents are cheap, screw into ordinary sockets and are perfectly adequate for a single animal in a small enclosure. They are a point source, they run warm, and their coverage falls off sharply away from the bulb. UVB LED bulbs and bars sit in between: better efficiency than a CFL, measurable and selectable UVI output, no bulb changes, but no heat at all and, on some models, no water resistance for humid setups.
On the general question of what UVB lighting is best across reptile groups, linear T5 HO tubes from the established brands remain the standard, with percentage chosen by species and enclosure depth. For a beginner assembling a first indoor enclosure, our sequence is simple: a T5 HO kit, a halogen basking lamp on a thermostat for an enclosed setup, and a plug-in timer.
Where to Mount Your UVB Lamp and How Long to Run It
Mount the lamp 10 to 20 inches above the top of the shell, with nothing between them. No glass, no mesh panel, no plastic sheet and no branch positioned in the light path. Every layer costs you UVB, and this is where I see setups quietly underperforming despite a good lamp.
Run it for 12 hours a day, controlled by a plug-in timer: on in the morning, off at night. That matches the photoperiod most species experience and keeps the circadian rhythm steady. If you want to automate the rest of the lighting, our guide to continuous lighting kits for beginners covers the timer and dimming side of a setup.
Distance and wattage interact. A stronger tube can safely sit higher, which is why a 10% or 12% lamp at 20 inches and a 5% lamp at 12 inches can land on similar UV indices. If you use the modes on the LED bar, treat them as the primary control and adjust distance second. And keep mercury vapour lamps further away than fluorescents, because their radiant heat is the larger risk.
Replace fluorescent tubes at 6 to 12 months. The 6 to 12 month advice from the manufacturers on this list is not hedging; a tube is often visibly dimmer at 12 months and still delivering useful UVB, while by 18 months it is meaningfully weaker. Six months suits a tube run at a long distance or in a hot enclosure, and twelve suits a tube run cool and close. LED fixtures are replaced on a far longer cycle.
Zoo Med ReptiSun vs REPTI ZOO: Which Brand Should You Buy?
The two brands on this list cover opposite ends of the market, so the comparison is mostly about format. Zoo Med ReptiSun sells established linear T5 HO tubes in defined percentages, with the brand used and recommended by zoos and veterinary practices. REPTI ZOO sells complete kits, mercury vapour lamps and mixed packs that bundle heat and UVB together.
Map percentages before you compare. A ReptiSun T5 HO 5.0 is the mid-strength linear tube and is the sensible default for Mediterranean species. The 10.0 desert tube is stronger and is what desert keepers reach for. If your comparison involves other brands, the widely repeated mapping is roughly Arcadia 6% to ReptiSun T5 HO 5.0 and Arcadia 12% to ReptiSun T5 HO 10.0, though a distance chart from the manufacturer is always the safer authority.
One caution on the branded comparison pages you will find. Tortoise Town states plainly that they recommend Arcadia over ReptiSun because of longer life and a spectrum closer to natural sunlight, but that assertion comes with no measurements behind it. Long-term keepers on tortoiseforum.org simply split, with one noting the Zoo Med 10.0 HO works while preferring Arcadia 12% tubes. I would size the lamp to your enclosure and measure the result rather than pick on brand reputation.
How to Tell Your UVB Light Is Working
Start with the packaging. Quality UVB lamps ship with a UV index graph showing measured output across a range of distances, and that curve is the most reliable guide you will get without a meter. Find your intended mounting height on the axis and read the index at the shell height your animal actually reaches.
A UV meter card or solar meter gives you a single-answer spot check. Hold it at the shell height under the lamp and compare the reading to the expected index for your species. Repeat it at the far end of the enclosure to find out whether coverage is even or whether the tortoise is only getting UV in one corner.
Test the same way every few months. The most common failure is not a dead bulb, it is a working bulb delivering weaker UV than it used to, and the only way to notice is to measure. Replacing the tube once it stops producing an appropriate reading at shell height keeps your calendar ahead of the problem rather than behind it.
Frequently Asked Questions
What UVB light is best for tortoises?
A linear T5 HO fluorescent tube is the best UVB light for most indoor tortoises because it spreads UVB evenly across the whole basking area. Mercury vapour suits large open-topped setups. Run the lamp 12 hours a day on a timer and mount it 10 to 20 inches above the shell.
What UVB wattage do tortoises need?
Match tube wattage to enclosure footprint rather than to the animal. One 24W to 32W T5 HO tube covers a 2 by 2 to 4 by 2 open area. A 23W compact or 5W UVB LED suits a single animal in a small enclosure. Two tubes or a 48W to 54W unit cover wider tables.
How long should I leave my UVB light on for my tortoise?
Twelve hours of light per day, controlled by a plug-in timer. Switch it on in the morning and off at night to match the photoperiod most species experience and keep the animal’s circadian rhythm steady. LED bars with a built-in day-night timer handle this automatically.
What is the difference between UVB and UVA light for tortoises?
UVA drives vision, colour perception and circadian rhythm, and most visible or LED lamps supply it. UVB drives vitamin D3 synthesis and calcium absorption, and only true UVB output delivers it. An LED that emits only UVA is not UVB lighting and will not prevent metabolic bone disease on its own.
Is UVB and basking light the same thing?
No. UVB is a light spectrum and basking heat is infrared warmth, so they come from different bulbs. The exception is a mercury vapour lamp, which produces both from one bulb. Because it cannot be thermostatted, a mercury vapour lamp only suits an open-topped enclosure.
Conclusion
One decision rule takes you most of the way: for an indoor tortoise, run a linear T5 HO tube on a 12-hour timer, mounted 10 to 20 inches above the shell, with a separate basking heat source on a thermostat if the enclosure is closed. Everything else on this list is a variation on that arrangement rather than a replacement for it.
Our pick at number one is the LUCKY HERP 23W 10.0 UVB compact fluorescent, which pairs broad availability with desert-strength output at a low running cost. If you would rather buy one complete package and have something that works immediately, the Zoo Med 5.0 T5-HO hood with its fitted lamp is the tidiest option. Whichever you choose, verify the output at shell height before you trust it, and replace it on schedule rather than when it starts to look dim.