Picking a UVB light for bearded dragon keepers is the one decision in the whole setup that nobody agrees on. Tube or bulb, T5 or compact, 12 inch or 22, and every forum thread contradicts the last one.

I should say this straight away: I do not keep a bearded dragon. I keep a desert tortoise that wandered into our yard in Henderson years ago and never left, and that is why I read UVB listings at all.

So I did what I do with any part I do not know well enough. I spent a full day on every UVB light worth buying now, eleven of them, reading the listings, the wattages, the stated UVB output and the reviews at both ends. I spent years as a mechanic in an off-road shop, so what I am good at is the hardware: the ballast, the reflector, the socket, the clips that hold it up. These are my picks.

Short version. The fixtures are where the interesting products are, and every one of them has a short track record. The two lamps thousands of owners have actually proven are both compact bulbs. And the single most common reason a new UVB light appears to be dead is a piece of blue plastic film nobody peeled off.

UVB light for bearded dragon setups, a beardie basking under its lamp
The whole point of the purchase. Photo: Matthew Jesus, Pexels.

Part of our reptile guides.

Quick picks: the best UVB light for bearded dragon setups

In a hurry? The best UVB light for a bearded dragon in most homes is the Zoo Med ReptiSun 10.0 Mini Compact, because it is the most reviewed UVB lamp there is and it fits a dome you probably already own. If you want a tube across the enclosure, the REPTIDLDB 24 watt T5 kit is the 22 inch fixture I would start with. The best long-term buy is a cheap fixture with a Zoo Med T5 HO tube in it.

You need My pick Why
The safest bet, full stop Zoo Med ReptiSun 10.0 Mini Compact The most reviewed UVB lamp here, 10% UVB stated
A tube for a 40 gallon REPTIDLDB 24W T5 kit 22 inch tube, fixture and bulb in one box
A tube for a 120 gallon Homnebila 24W T5 22 inch, reflective coating, three mounting options
Best value LUCKY HERP 10.0, 23 watt Second most reviewed lamp here, 10% UVB stated
Replacing a tube you already have Zoo Med T5 HO ReptiSun 10.0 The name keepers trust, and it ships as a pair
A small or starter enclosure REPTIDLDB 8W T5, 12 inch The cheapest real fixture on this page
A fixture that takes name-brand tubes QZQ 8W T5 kit Owners report standard tubes drop straight in
The best reflector on a budget kit GREENPAW T5 combo Polished curved reflector, three mounting methods
A spare bulb in the cupboard Jugbuy 23W spiral, two pack Two bulbs, 10% UVB and no UVC stated

How I ranked these UVB lights

I cannot measure UVB output and I am not going to pretend otherwise. What I can do is read every listing properly, sort what the maker actually states from what it implies, and read the reviews at both ends. Everything below is either printed on the listing or reported by an owner, and I say which.

  • What the maker actually prints. A stated 10.0 or 10% UVB figure beats a paragraph about desert sunshine. Several lamps here talk about output and never print a number.
  • Fixture or bulb. A combo kit is a fixture, a tube and the clips in one box. A bulb on its own needs a dome or a hood you already own.
  • The hardware. Ballast, reflector, end caps, cord and mounting. This is the part I know, and it is the part that separates these kits.
  • Length against enclosure. A stated tube length in inches, so you can match it to your tank instead of guessing.
  • What owners report after months. Lifespan is the complaint in this whole category, on cheap fixtures and famous bulbs alike.

Straight talk: I earn a commission if you buy through my links. It costs you nothing, and it is why I can spend a day reading reptile lighting listings. Prices change hourly, so I do not print them. Click through and check. Nothing here is veterinary advice, and any figure about your animal’s care should come from your vet or the maker’s own instructions.

Best T5 UVB fixture kits for a bearded dragon

This is where the category has moved. A combo kit gives you a housing, a linear tube and the mounting hardware in one box, so the light spreads down the enclosure instead of sitting in one hot circle. Read the records here honestly. Every fixture on this page is a young product with a short track record, and lifespan is the recurring gripe on all of them.

REPTIDLDB 24 watt T5 UVB reptile light fixture combo kit with 22 inch tube
Best T5 kit40 gallon pick

1. REPTIDLDB 24W T5 UVB Fixture Combo Kit

  • 22 inch tube, 24 watts
  • 10% UVB and 30% UVA output stated
  • Built-in T5 HO electronic ballast
  • Mounts on mesh or inside the lid

The fixture I would buy first for a standard four foot enclosure. Everything in one box, a real T5 HO ballast, and a stated output figure rather than a paragraph of marketing.

Check the price on Amazon

Owners like the spread. A Hermann’s tortoise keeper calls it easy to install and says it lights the whole enclosure. A bearded dragon owner says his dragon approves, which is the review you want. One buyer says it has lasted longer than any other he has bought. And one left a note everybody should read: peel the blue film off the inside.

The gripe is the one that runs through this whole section. Several owners report about four months of life, and one who said do not buy updated his review after the seller replaced the bulb without a fight. Buy from a seller with a live returns window and keep the packaging for a month.

What bugs me

  • Owners report failures around four months
  • No replacement interval printed anywhere
Homnebila T5 10.0 UVB reptile light fixture, 24 watt 22 inch
120 gallon pick

2. Homnebila T5 10.0 UVB Fixture, 24W

  • 22 inch fixture, 24 watts
  • High reflectivity coating stated
  • Flicker-free T5 HO ballast, insulated end caps
  • Three mounting options, 5.9 foot cord with a switch

The best hardware story of the fixtures here. Reflective coating, insulated end caps, an inline switch and three ways to hang it, which matters on a big enclosure.

Check the price on Amazon

Two owners tested theirs with a UV card and both were satisfied. One says it runs the full length of a 40 gallon enclosure for a beardie. Another hung his from a screen top and says it covers almost the entire length of a four foot cage, which is the 120 gallon answer.

Then the other end. One owner calls it dim and says it failed after two days. That is a single report against several good ones, but it is the failure mode to watch, so open the box and run it before you rely on it. The maker claims a large multiple of the UVB output of a standard hood, and I have no way to check that, so treat it as a claim rather than a fact.

What bugs me

  • An early failure report inside two days
  • The output multiple is a claim with no test behind it
Terrarium with a light hood fitted over the mesh top
A linear tube spreads light down the enclosure instead of into one circle. Photo: Nikita Korchagin, Pexels.
REPTIDLDB 8 watt T5 10.0 UVB reptile light fixture, 12 inch
Best cheap fixture

3. REPTIDLDB 8W T5 UVB Fixture, 12 inch

  • 12 inch tube, 8 watts
  • 10% UVB and 30% UVA output stated
  • T5 HO electronic ballast, no flicker reported
  • Sits on the mesh or fits inside a vivarium

The small version of the kit at number one, and the cheapest genuine fixture here. For a starter tank or a smaller enclosure, this is the entry point.

Check the price on Amazon

The install is what owners praise. One calls it nice quality and simple, with a choice of ways to fix it to the cover. Another has run his five months with no flicker and a one button switch, and says his Hermann’s tortoise loves it. A third says the listing details were accurate, which is rarer than it should be.

Two honest warnings. It is eight watts, so it is a small enclosure light and owners who expected more say so. And the reliability and lifespan complaints are the loudest of any fixture here, including one that stopped after two months. If your enclosure is four feet, skip this and buy a 22 inch fixture instead.

What bugs me

  • The heaviest lifespan complaints on the page
  • Eight watts and 12 inches is a small tank only
GREENPAW T5 UVB reptile light fixture combo kit with curved reflector
Best reflector

4. GREENPAW T5 UVB Combo Kit, 8W

  • 12.44 inch aluminium hood, 8 watts
  • 10.0 bulb, hood and mounting accessories included
  • Polished curved reflector stated
  • Flame retardant end covers, three mounting methods

The best built of the small kits. An aluminium hood for heat dissipation, a polished curved reflector, and every piece you need in the box.

Check the price on Amazon

The reviews are short and consistent. One keeper says his reptile became noticeably more active after switching to it. A Sulcata owner calls it perfect for his tortoise and points out it ships with a UVB test card so you can confirm the lamp is doing something. That test card is a genuinely good inclusion.

The same Sulcata owner also left the warning of the day. He forgot to remove the blue plastic and wondered why it was not emitting UVB. This is the third listing on this page where that happened. The real caution is the record: this is a young product with few reports behind it, so treat it as promising rather than proven.

What bugs me

  • A short record, few owner reports so far
  • Eight watts, so it is a small enclosure light
JHGKEGKE T5 10.0 UVB reptile light fixture combo kit with detachable cord
Long spread pick

5. JHGKEGKE T5 10.0 UVB Combo Kit, 8W

  • 12.4 inch fixture, 8 watts
  • 10% UVB and 30% UVA stated
  • Alloy reflective layer, curved reflector
  • Detachable 5.9 foot cord, flame retardant end covers

The detachable cord is the detail I like. It makes the fixture easier to move, store and fit, and it is the kind of thing you only appreciate the third time you rearrange an enclosure.

Check the price on Amazon

Owners rate the light spread above everything. One says it covers his whole turtle tank and is bright and durable, and adds a sensible tip: secure it properly, because if it goes in the water it is finished. He taped the unplugged end to the tank side. Another, who says he has used around twenty different UVB brands, calls the length and spread excellent and the brightness great.

That same experienced owner names the two omissions: no timer and no spring hooks. And the reliability reports split, with more than one owner losing theirs at around four months. Put it on a plug-in timer you buy separately and mount it properly from day one.

What bugs me

  • No timer and no spring hooks included
  • Failures reported around the four month mark
QZQ T5 10.0 UVB reptile light fixture combo kit, 8 watt
Takes name-brand tubes

6. QZQ T5 10.0 UVB Combo Kit, 8W

  • 8 watts, 10% UVB and 30% UVA stated
  • Polished curved alloy reflector
  • 5.9 foot detachable cord with a switch
  • Flame retardant covers, multiple mounting accessories

I am including this one for a specific reason, and it is not the reviews. Owners report it accepts standard name-brand tubes, which turns a cheap housing into a long-term fixture.

Check the price on Amazon

That is the whole argument. One owner calls it an affordable alternative to the big names and says plainly that it fits main brand bulbs. Another had his a week, found it easy to assemble and surprisingly bright for a 12 inch unit at eight watts, and left the same reminder as everyone else: take the blue plastic film off the reflector.

Now the part I will not soften. This is the lowest rated product on this page and the complaints are blunt. One owner calls the build cheap, says it is dim, and recommends a premium brand instead. Buy this as a housing for a better tube, not as a finished lamp, and if you want it to be a finished lamp, buy number one instead.

What bugs me

  • The lowest rated product on this page
  • Owners call the supplied bulb dim and the build cheap

The replacement T5 tube, if you already own a fixture

Every fixture above is a housing with a tube in it, and the tube is the part that fades. This is the one most keepers name when you ask what they put in the housing.

Zoo Med 24 watt T5 HO ReptiSun 10.0 UVB lamp, two pack
Premium pick

7. Zoo Med T5 HO ReptiSun 10.0, 24W, two pack

  • 24 watt T5 HO linear tube
  • 10.0 UVB lamp, high output
  • Ships as a pair, so you hold a spare
  • Bulb only, needs a T5 HO fixture

The tube keepers name without being asked. It carries the best rating on this page and it is the one product here with a brand behind it rather than a listing.

Check the price on Amazon

The long-term reports are what sell it. One owner has run these for five years for his bearded dragon, noticed a new batch glowed slightly purple, contacted the maker and got an answer. Another says the guidance is to replace them every six months and that his have run well past a year. A third could see his old tube was no longer producing and ordered these as the replacement he trusted.

Two things to know. Reliability is the single biggest theme in the feedback, and it cuts both ways: plenty say they work perfectly, and a real number report a tube dead out of the box. Test a new one immediately so you are inside the returns window. And this is a bulb, not a kit, so you need a T5 HO fixture already.

What bugs me

  • Dead-on-arrival reports turn up regularly
  • Bulb only, and the priciest thing here

Compact and coil UVB bulbs for a bearded dragon

A compact bulb screws into a dome lamp and puts UVB into one area rather than along a tube. This is where the proof is. The two most reviewed lamps on this entire page are both compacts, which is worth knowing before you assume a tube is automatically the better buy.

Zoo Med ReptiSun 10.0 Mini Compact Fluorescent UVB lamp, 13 watts
Best all-roundMost reviewed

8. Zoo Med ReptiSun 10.0 Mini Compact, 13W

  • 13 watts, mini compact fluorescent
  • 10% UVB and 30% UVA output stated
  • UVB transmitting quartz glass
  • Mounts vertically or horizontally

The most reviewed UVB lamp in this whole crawl, by a wide margin. If you want the option the largest number of keepers have actually lived with, this is it.

Check the price on Amazon

It turns up in every kind of enclosure. A grandparent bought one for a hatchling turtle and found it cheaper than the identical bulb locally. A gargoyle gecko keeper says the temperature suits a species that is fussy about it. Several owners simply say it lights up and works, which after a day of reading lighting listings is a compliment.

Now the honest half, because the volume of feedback here is enormous and it is genuinely split. Functionality and lifespan are the two biggest themes and both cut both ways. One thorough owner reports output dropping off sharply by six months and rates a rival brand as lasting longer. Others say it burned out inside a month, and a few say it is no brighter than a night light. Buy it, test it early, and plan on replacing it more often than you would like.

What bugs me

  • Owners report output fading well before failure
  • Early burnouts turn up often in the feedback
LUCKY HERP UVA UVB 10.0 desert compact fluorescent reptile lamp, 23 watts
Best value

9. LUCKY HERP UVA UVB 10.0, 23W

  • 23 watts, desert 10.0 compact fluorescent
  • 10% UVB and 30% UVA output stated
  • Low UVB degradation claimed by the maker
  • Aimed at desert species including bearded dragons

The second most reviewed lamp here and the value pick. More wattage than the Zoo Med mini for less money, with the same stated output figures.

Check the price on Amazon

The best review here is also the most useful. An owner was given a bulb by a seller who said it was UV, checked it, and found it was not. Two days under this one and he says his dragon looked like a different animal. Another says it made his dragon’s colours pop and it was still going strong three or four months in, with an occasional flicker at switch-on.

Lifespan is again the split. One owner’s bulb lasted a month, though he rates the company highly for refunding him without argument. Another had his stop, then start working again weeks later on its own, which is the sort of thing that tells you these are built to a price. Good after-sales service is a real part of the value here.

What bugs me

  • Short-life reports, including inside a month
  • Some flicker on switch-on
Reptile lamp fixture mounted over a habitat
A compact bulb needs a dome. A tube needs a hood. Work out which you own before you order. Photo: Aibek Skakov, Pexels.
Jugbuy 23 watt UVB 10.0 spiral compact fluorescent terrarium lamp, two pack
Two pack pick

10. Jugbuy 23W UVB 10.0 Spiral, two pack

  • 23 watts, E26 base, 110 to 130 volts
  • 10% UVB and 30% UVA, no UVC output stated
  • UVB transmitting quartz glass
  • Two bulbs in the box

The only listing here that states plainly it puts out no UVC, and it ships as a pair. Buying two at once is the sensible way to own a consumable.

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The standout report is one owner whose first bulb ran over three years, which he rightly calls great value. Another says they work well for his bearded dragon. A third notes it fits a standard Zoo Med dome, which is exactly the compatibility question you want answered before ordering.

Against that, one owner got two months before it burned out and describes the light as merely okay, and notes it runs warm under your hand. The spread between three years and two months on the same bulb is the honest summary of this whole category. The two pack softens the blow.

What bugs me

  • Lifespan reports swing wildly, months to years
  • Only a one month quality assurance window stated
Hygger zoo UVA UVB 10.0 reptile light bulb, 26 watts
Cheapest here

11. Hygger zoo UVA UVB 10.0, 26W

  • 26 watts, the highest wattage compact here
  • 10% UVB and 30% UVA output stated
  • Premium quartz glass stated
  • Aimed at desert terrarium species

The cheapest lamp on this page, listed here so you can see it properly rather than find it on your own. I am not recommending it, and the reason is in the second paragraph.

Check the price on Amazon

Plenty of owners are happy. One keeps Pac-Man frogs, has bought three and reports no problems. Others say it is exactly as listed and good quality for the money. On wattage alone it is the biggest compact bulb here.

Here is the report that keeps it out of my picks. One owner walked into a room of enclosures, found a strong electrical burning smell and traced it to this bulb in a dome he had used without issue for years. He replaced it with a name-brand bulb and the problem went. That is one owner’s account, not a test I ran, and durability complaints are the largest single theme in this listing’s feedback. Follow the maker’s instructions, use a dome rated for the wattage, and I would spend a little more elsewhere.

What bugs me

  • Durability is the biggest theme in its feedback
  • An owner reported a burning smell and stopped using it

T5, T8 and compact, in the makers’ words

T5 is what the fixtures here sell. Every linear kit on this page is described as T5 HO, meaning high output, and each one states 10% UVB and 30% UVA. The tube is slimmer than the older standard and the listings all pair it with an electronic ballast built into the housing.

T8 is the older tube, and here is the finding. Not one T8 product came back in this crawl. Not a single seller in the set I looked at is pushing a T8 fixture or tube for a bearded dragon. The makers have moved the category to T5 HO and their own listings say so. If you own a T8 hood already, you are running a format the sellers have quietly stopped promoting.

Compact means a screw-in bulb. The two compacts with the deepest records both state the same 10% UVB and 30% UVA as the tubes, and both use what the makers call UVB transmitting quartz glass. What changes is the shape of the coverage, not the printed output figure: a bulb lights an area under a dome, a tube runs the length of the enclosure.

Fixture or bulb comes down to what you own. A combo kit is the answer if you have nothing, because the housing, the tube and the clips arrive together. A bulb on its own is the answer if you already have a dome or a T5 hood. And the shape I would actually buy, based on what owners report, is a budget housing with a name-brand tube in it. One QZQ owner confirms standard tubes drop into these cheap fixtures, which means the housing and the consumable can be bought separately and replaced on different schedules.

What size UVB light for a 40 gallon and a 120 gallon

This is the question page one does not answer, so let me do it with the only numbers I am willing to use: the tube lengths the makers print.

For a 40 gallon. A standard 40 gallon breeder is 36 inches long. The 22 inch fixtures here, numbers one and two, are the closest fit in this set, and an owner of number two confirms his runs the full length of a 40 gallon enclosure for a beardie. The 12 inch kits at numbers three, four, five and six will light a section rather than the run. On a compact bulb, the mini compact at number eight is the one keepers of smaller setups name most.

For a 120 gallon. A 120 is typically four feet long and this is where the small kits stop being sensible. The 22 inch fixtures are what you want, and an owner of number two says his covers almost the entire length of a four foot cage hung from the screen top. The maker of the fixture at number one states the same housing is sold in 34 inch and 46 inch versions with higher wattages, so if you want a single tube down a four foot enclosure, that longer version is the thing to order rather than the 22 inch one reviewed here.

On wattage. The linear fixtures here run 8 or 24 watts and the compacts run 13 to 26. Higher wattage is not the same as more UVB at your animal, because distance and the mesh above the enclosure both change what arrives. For how far above the basking spot to mount it and how long to run it, follow the maker’s own instructions for the exact lamp you buy and your vet’s guidance for your animal. I am not going to invent a number for you, and you should be wary of anyone who does.

UVB light feature check table

Every lamp here, every feature that comes off the listing, one screen. Scroll sideways on a phone.

Lamp T5 tube Fixture included Bulb in the box 10.0 or 10% stated Length stated 22 inch or longer Replacement interval stated Reflector stated Mounting hardware stated
1. REPTIDLDB 24W T5 n/s n/s
2. Homnebila 24W T5 n/s n/s
3. REPTIDLDB 8W T5 n/s n/s
4. GREENPAW T5 combo n/s
5. JHGKEGKE T5 combo n/s
6. QZQ T5 combo n/s n/s
7. Zoo Med T5 HO ReptiSun n/s n/s n/s
8. Zoo Med Mini Compact n/s
9. LUCKY HERP 10.0 n/s
10. Jugbuy 23W spiral n/s
11. Hygger zoo 26W n/s

n/s = the maker does not say. Every check comes from the listing text, never from a review and never from me. “T5 tube” is a check only when the listing says T5. “Fixture included” is a check when a housing is sold, and a cross when the product is a bulb alone.

“Bulb in the box” is a check when a bulb ships in the package. “10.0 or 10% stated” needs that figure printed on the listing. “Length stated” needs a measurement in inches. “Replacement interval stated” needs a printed interval, and no listing here has one. “Reflector stated” needs a named reflector or reflective coating. “Mounting hardware stated” needs named clips, brackets, a hood mount or a hanging kit.

When to replace a UVB bulb, as each maker states it

Here is the real finding, and it surprised me. Look at that column in the table. Not one of these eleven listings prints a replacement interval. For a product whose entire failure mode is fading quietly while still lighting up, that is a serious gap in how these are sold.

What owners report fills in the rest. An owner of the Zoo Med tubes says the guidance he was given is every six months, and adds that his have run well past a year. A thorough owner of the mini compact reports output dropping off sharply by around six months and rates a rival brand as holding on longer. Owners of the fixtures report failures clustered around four months, and one owner of the Jugbuy spiral got over three years out of his first bulb.

The trap is that a UVB lamp does not tell you. It keeps producing visible light long after the useful output has fallen away, so the lamp looks fine while doing less and less. That is why every experienced keeper in these reviews talks about a schedule rather than waiting for a failure.

Three things I would do, all of them hardware habits rather than care advice. Buy in pairs where the listing offers it, so the replacement is already on the shelf. Write the fitting date on the base of the bulb with a marker, because you will not remember. And buy a UVB test card if your lamp does not include one, since two of the kits here ship with one and owners used them to confirm the lamp was working. For the interval itself, follow the instructions that come with the exact lamp you buy and ask your vet what suits your animal.

My top 3 UVB lights for a bearded dragon

Eleven lamps is a lot, so here is where I would spend money, one at each price. One thing to be upfront about. Every T5 fixture kit on this page carries a short record, and the two products thousands of owners have genuinely proven are both compact bulbs. That is why my top three looks the way it does rather than leading with the newest fixture.

Premium pick
Zoo Med T5 HO ReptiSun 10.0 UVB lamp two pack

Zoo Med T5 HO ReptiSun 10.0

The best rated lamp here and the one keepers name unprompted, with owners running them for years. Ships as a pair. You need a T5 HO fixture to put it in, and any of the kits above will do that job.

Check the price on Amazon

Best all-round
Zoo Med ReptiSun 10.0 Mini Compact UVB lamp

Zoo Med ReptiSun 10.0 Mini Compact

The most reviewed UVB lamp in this whole set, 10% UVB printed on the listing, and it screws into a dome you probably already own. Replace it on a schedule and it is the least risky purchase here.

Check the price on Amazon

Best value
LUCKY HERP UVA UVB 10.0 desert compact fluorescent reptile lamp

LUCKY HERP UVA UVB 10.0, 23W

The second deepest record on this page, the same stated output as the premium mini compact, more wattage and less money. Owners report the seller sorts out a short-lived bulb without an argument.

Check the price on Amazon

Notice what is not here: the cheapest one. The Hygger at number eleven is the lowest priced lamp on this page, and it is also the one where an owner reported an electrical burning smell and stopped using it. The QZQ kit at number six is the cheapest way into a T5 housing and it is the lowest rated product here, which is exactly why I recommend it as a housing for a better tube rather than as a finished lamp.

Lighting is one part of the enclosure. The lamp has to hang over something, so our bearded dragon tank guide is the next thing to read, our tortoise enclosure guide covers the housing side for the species I actually keep, the rest of the reptile guides cover the other setups, and keeping any enclosure clean is easier with the right pet cleaning supplies.

Bearded dragon close up, the reptile a UVB light is for
Buy the lamp for the animal, then replace it on a schedule. Photo: Lily, Pexels.

UVB light for bearded dragons FAQ

What watt UVB bulb does a bearded dragon need?

The lamps here run 8 or 24 watts as linear T5 tubes and 13 to 26 watts as compact bulbs. Wattage is not a measure of UVB reaching your animal, because mounting height and the mesh over the enclosure both change that. Match the tube length to your enclosure first, then follow the maker’s instructions for the lamp you buy.

What does 10.0 mean on a UVB light?

On these listings 10.0 is the desert grade, and the makers that print an output figure alongside it state 10% UVB and 30% UVA. The same makers offer a 5.0 version described as being for tropical species such as chameleons and frogs, and describe 10.0 as being for desert dwellers including bearded dragons and tortoises.

Do I need a 70 watt UVB bulb?

Nothing in this set is a 70 watt UVB lamp. That figure usually belongs to a mercury vapour lamp or a heat bulb, which are different products doing a different job. Every UVB lamp here is either a T5 HO tube at 8 or 24 watts or a compact bulb between 13 and 26.

What UVB light do I need for a 40 gallon tank?

A 40 gallon breeder is 36 inches long, so a 22 inch T5 fixture like number one or number two covers most of the run, and an owner of number two confirms his does exactly that. A 12 inch kit lights a section rather than the length. A compact bulb in a dome is the alternative if you would rather light the basking area only.

What UVB light do I need for a 120 gallon tank?

A 120 is usually four feet long, so the small kits are the wrong tool. A 22 inch T5 fixture is the starting point, and an owner reports his covers almost the whole length of a four foot cage hung from the screen top. The maker of number one states the same fixture is sold in 34 inch and 46 inch versions at higher wattages, and that is the better order for a four foot enclosure.

Is a T5 UVB light better than a compact bulb?

The makers have clearly moved to T5 HO, and not one T8 product came back in this crawl at all. What the listings do not show is a difference in printed output: the tubes and the best compacts both state 10% UVB and 30% UVA. The real difference is coverage, a tube along the enclosure against a bulb over one area. If your new lamp seems dead on arrival, before anything else check whether the blue protective film is still stuck on the reflector, because owners of three separate fixtures here made exactly that mistake.