Most reptiles that die badly in a UAE flat die of one of two things: they could never get warm enough in a way they controlled themselves, or they never received usable UVB. Both are equipment problems. Both are cheap to fix. But almost every "starter kit" sold with a vivarium gets at least one of them wrong, usually by bundling a single bulb that pretends to do both jobs and does neither well.
This article is the equipment half of reptile keeping — the lighting and heating pillar that sits underneath every species guide on this site. If you want the numbers for one particular animal, the species guides have them: bearded dragons, leopard geckos, tortoises and turtles each have their own targets. What follows is the part they all share.
Quick answers
Does a heat lamp give UVB?
No. An ordinary halogen or incandescent basking bulb produces essentially zero usable UVB. Only a bulb specifically sold as UVB — a linear T5 or T8 tube, a compact coil, or a mercury vapour lamp — produces it. Heat and UVB are two separate purchases for most setups.
My UVB bulb still lights up. Do I really need to replace it?
Yes. Visible light and UVB output decay on completely different curves. A tube can be producing near-zero UVB while looking exactly as bright as the day you bought it. Replace T5 tubes every 12 months and T8 tubes and compacts every 6 months, and write the date on the bulb in marker the day you install it.
Is a thermostat optional if I use a low-wattage bulb?
No. A heat source without a thermostat is a device whose only setting is "full power forever." Ambient temperature in a UAE home swings hard between an AC'd afternoon and a switched-off night, and an unregulated heat mat or ceramic emitter will happily cook an animal that has nowhere else to go.
Can I put the UVB tube on top of the mesh lid?
You can, and most people do, but understand the cost: standard vivarium mesh blocks roughly 30–50% of the UVB passing through it. Mount above mesh and you need to shorten the distance to the basking spot to compensate, or step up a bulb strength.
What is the single most common fatal mistake?
A vivarium that is one uniform temperature. Reptiles do not have a thermostat inside them — they have legs. If the whole enclosure is 34 °C, the animal cannot cool down, and if the whole enclosure is 24 °C, it cannot digest. The gradient is the point.
Two different jobs: light they can use, and heat they can escape
Everything in this article serves one of two functions, and confusing them is where most setups go wrong.
UVB is a chemistry supply. UVB in the 290–315 nm band drives the conversion of a precursor in the skin into vitamin D3, which in turn allows the animal to absorb calcium from its gut. No UVB and no dietary D3 means calcium goes in the mouth and straight out the other end, the body starts pulling calcium out of the skeleton, and you get metabolic bone disease — the wobbly limbs, rubbery jaw and twitching that show up in six to eighteen months and are only partly reversible. It is slow, silent and completely preventable. The diet side of the same equation is covered in the calcium and gut-loading guide; UVB is the other half, and neither works properly without the other.
Heat is a metabolic switch. Reptiles are ectotherms: digestion rate, immune function and activity all track body temperature, and body temperature tracks where the animal chooses to sit. Your job is not to hold the box at a number. Your job is to build a range wide enough that the animal can pick its own number, hour by hour.
UVB is not heat, and heat is not UVB
The one product that genuinely does both is a mercury vapour bulb, which emits UVB, UVA, visible light and a lot of heat from a single fitting. It is convenient and it is also the least controllable option you can buy, because you cannot dim it or thermostat it without destroying it — the arc needs full voltage to strike and stay lit. That means the only way to adjust its output is to physically move it, and the only way to shut it off is to leave the animal with no UVB. For most keepers, separating the two jobs into a UVB tube plus a separately controlled heat source is easier, safer and cheaper to run.
Choosing a UVB source
Tube, compact or mercury vapour
A linear T5 HO tube is the default answer for almost every diurnal reptile. It throws UVB across a long strip rather than a hot spot, which means the animal gets a usable dose while moving around normally instead of having to sit on one exact tile. Run it in a reflector fixture — a bare tube wastes more than half its output upward into your ceiling, and a good reflector roughly doubles what reaches the animal.
T8 tubes are the older, lower-output version. They still work for shallow enclosures and lower-requirement species, but they need to be closer to the animal and replaced twice as often.
Compact coil bulbs screw into a normal lamp holder, which makes them tempting. They produce a narrow, intense cone of UVB directly under the bulb and almost nothing a hand's width away. They are acceptable as a supplement in a small enclosure for a low-requirement animal, and a poor primary source for anything else.
Mercury vapour suits large, tall, bright enclosures — a big tortoise table or a walk-in style setup — where you want a strong beam covering a long vertical drop. In a 120 cm glass terrarium in an air-conditioned flat, it is usually more lamp than the space can handle.
Which strength: 5%, 6%, 10% or 12%
The percentage on the box is the proportion of the bulb's output in the UVB band, and it is only meaningful together with a mounting distance. Broadly:
- 2–6% ("forest" / "tropical") — crested geckos, day geckos, rainforest species, most amphibian-style setups, young animals in heavily planted enclosures.
- 10–12% ("desert") — bearded dragons, uromastyx, tortoises, and anything else that would be sitting in open sun in the wild.
- Nocturnal species — leopard geckos and similar were long kept with no UVB at all. Current practice is a low-output tube on a normal day cycle, which the animal can avoid if it wants to. It is a benefit, not a requirement, and it must never come with a hot spot they cannot leave.
Distance is half the dose
UVB falls off with distance faster than most people expect — roughly with the square of the distance, so doubling the gap cuts the dose to about a quarter. This is why "I bought the 12% tube" tells you nothing on its own. A 12% T5 mounted 45 cm above a basking rock and a 6% T5 mounted 25 cm above the same rock can deliver a similar dose.
The practical version: mount the tube so that the animal's back, when it is sitting in its normal basking pose, is roughly 25–40 cm from a T5 HO tube, or 15–25 cm from a T8, and check the manufacturer's own distance chart because they genuinely differ between brands. Then make sure the animal cannot climb closer than the minimum safe distance — a branch or a stack of rock that puts a dragon 8 cm from a tube is an eye and skin problem waiting to happen.
Mesh eats UVB
Most vivarium lids are steel or aluminium mesh, and mesh blocks 30–50% of the UVB depending on how fine it is. If your tube sits on top of the lid, treat the effective distance as longer than the tape measure says, and either move the basking site up or step the bulb strength up one notch. Mounting the tube inside the enclosure removes that loss entirely, but then it has to be sealed, out of reach of climbing animals, and clear of water — which is why most keepers accept the mesh penalty and compensate for it.
Glass and most acrylic block UVB almost completely. A UVB tube shining through the front pane of a terrarium is doing nothing at all.
Replacement: the bulb lights long after the UVB has gone
This is the single most under-communicated fact in reptile keeping. The phosphor that produces UVB degrades much faster than the phosphor that produces visible light. By month twelve a T5 may be putting out a fraction of its original UVB while looking identical. There is no visual cue, no flicker, no colour shift.
So use the calendar, not your eyes: T5 HO every 12 months, T8 and compacts every 6 months, mercury vapour every 12 months. Write the install date on the bulb with a marker, and set a repeating reminder on your phone the day you fit it. If you want certainty rather than a schedule, a UV index meter is the only way to actually measure it, and is worth it if you keep several enclosures.
Choosing a heat source
Overhead basking bulbs
A halogen or incandescent flood bulb in a ceramic-socket dome is the closest thing to sunlight: it produces a focused warm spot with a steep gradient around it, exactly the shape a basking animal evolved to use. Halogen is more efficient than old incandescent and produces a tighter beam. This should be the primary daytime heat source for basking species.
Wattage is set by the enclosure and the room, not by the animal. In an air-conditioned Dubai flat sitting at 23–24 °C, a 50–75 W halogen is often enough to make a proper basking spot in a 90–120 cm vivarium; in a villa room that sits at 28 °C you may need less. Always start lower than you think and measure.
Ceramic heat emitters
A CHE produces heat and no visible light at all, which makes it the correct choice for maintaining night-time ambient temperature or for holding background warmth in a species that should not have a bright light on it. It screws into a ceramic socket — never a plastic one, which will fail — and it stays dangerously hot to the touch for several minutes after switching off. It must be guarded if the animal can reach it, and it must be on a thermostat.
Heat mats
A mat under one end of the enclosure provides belly heat, which suits ground-dwelling and burrowing species. Two rules make them safe: they go under the enclosure or on an outside wall, never loose inside where an animal can lie directly on the element, and they go on a thermostat with the probe taped to the glass directly above the mat. An unregulated mat can reach temperatures that cause serious thermal burns through the substrate, and reptiles will not reliably move away — many species do not register belly heat as pain until damage is done.
A mat is a supplement for most basking species, not a replacement for an overhead source. Digestion in a bearded dragon or tortoise depends on warming the body core from above, and a warm floor alone does not achieve it.
Deep heat projectors
A DHP sits between a halogen and a CHE: no visible light, but it emits shorter-wavelength infrared that penetrates rather than only warming the surface. They are useful for night heat in species that need it and for supplementing a basking zone without adding brightness. They are more expensive and they still need a thermostat.
What not to use
Heat rocks are the classic hazard — a small element inside a fake stone with no reliable regulation, in direct contact with the animal. Skip them entirely. Coloured "night" bulbs, red or blue, are also worth avoiding: many reptiles see into those wavelengths, so you are not giving them darkness, you are giving them a permanently lit room. If you need night heat, use a CHE or DHP, which produce none.
The thermostat is the actual safety device
If you buy one thing properly in a reptile setup, buy the thermostat. Every heat source above is a resistor that converts electricity into heat until you stop it. The thermostat is the thing that stops it.
Matching the type to the heater
- On/off thermostats cut power completely at the setpoint and restore it when temperature drops. Fine for heat mats and CHEs. Poor for light-emitting bulbs, because the animal experiences the sun blinking on and off all day.
- Pulse proportional rapidly pulses power to hold a steadier temperature. Good for CHEs, mats and DHPs. Not for halogen or incandescent bulbs — the pulsing shortens their life dramatically and produces visible flicker.
- Dimming thermostats smoothly reduce voltage. This is the correct type for any light-emitting heat bulb, and it also works for CHEs and mats. If you only want to own one kind, own this one.
- Never thermostat a mercury vapour or fluorescent UVB bulb. Neither tolerates dimming or pulsing. UVB tubes go on a plain timer.
Where the probe goes
The probe location is the setting. A probe dangling in mid-air in the cool end will let the basking bulb run at full power all day; a probe taped to the basking rock directly under the lamp will shut the lamp off almost immediately and leave the rest of the enclosure cold.
The usual convention: for a basking lamp on a dimming stat, position the probe near the basking site but not in the direct beam, then set the stat so that the measured basking surface temperature lands on target. For a heat mat, tape the probe to the glass directly over the mat, inside the enclosure, under the substrate. In all cases, secure the cable so the animal cannot drag the probe somewhere else — a probe that has been shifted into a hide is how enclosures overheat overnight.
And then verify with something independent. A thermostat reports what its probe sees. A separate digital thermometer with a probe at the basking surface, plus an infrared temperature gun for spot-checking surfaces, tells you what the animal is actually experiencing. Stick-on dial thermometers are decorative and should not be trusted for anything.
The backup layer
Thermostats fail, and they usually fail on — a stuck relay means continuous full power. If you keep an expensive or long-lived animal, a second thermostat wired in series and set 3–4 °C above the primary costs very little and turns a fatal failure into an inconvenience. At minimum, use a timer on the basking circuit so that even a failed stat cannot run overnight.
Building the gradient
Put all heat at one end. All of it. The other end should be genuinely cool, with a hide at each end so the animal never has to choose between the temperature it wants and feeling safe. A hide only at the warm end forces a bad trade.
Rough targets for common species — always confirm against a current species guide, and measure surface temperature at the basking site rather than air temperature:
| Species | Basking surface | Cool end | Night | UVB |
|---|---|---|---|---|
| Bearded dragon (adult) | 38–42 °C | 24–27 °C | 18–22 °C | 10–12% T5 |
| Uromastyx | 43–49 °C | 26–29 °C | 20–24 °C | 12% T5 |
| Leopard gecko | 30–33 °C warm floor | 22–25 °C | 18–22 °C | Low-output, optional |
| Crested gecko | 26–28 °C max | 21–24 °C | 18–22 °C | 2–6% T5 |
| Mediterranean tortoise | 35–38 °C | 20–24 °C | 15–20 °C | 10–12% T5 |
| Sulcata / African spurred | 37–40 °C | 26–29 °C | 22–25 °C | 12% T5 |
| Red-eared slider | 32–35 °C dry dock | Water 24–27 °C | Ambient | 10% T5 over dock |
| Blue-tongue skink | 35–38 °C | 23–26 °C | 18–22 °C | 6–10% T5 |
Two notes on that table. First, a night-time drop is normal and usually beneficial — most species do not need supplemental night heat at all in a UAE home unless the AC drives the room below their minimum. Second, humidity interacts with all of this: the same basking bulb that is correct in a rainforest enclosure will strip a desert enclosure dry, or vice versa. That interaction is its own topic, covered in the desert species humidity guide and the rainforest terrarium setup guide.
The UAE-specific part
Your air conditioning is the winter
This is the piece that surprises people who learned reptile keeping from British or American sources. In the UAE, the hard season for a vivarium is not the one you would guess. Outdoors in July it is 45 °C; indoors, the AC is holding your flat at 22–24 °C for months on end, which is colder and far more constant than a European living room. Meanwhile in December and January many people switch the AC off entirely and windows come open, and the room drifts warm.
The consequences are practical. Your basking bulb will need to work harder in an air-conditioned August than in an unconditioned January. A setup dialled in during Ramadan may be wrong by mid-summer. And an AC vent blowing directly across a mesh lid will strip heat and humidity out of the enclosure fast enough to defeat any thermostat — move the enclosure or redirect the vent, do not just add wattage.
Practically: re-check your temperatures whenever the household AC pattern changes, and again at the start and end of summer. Twice a year, five minutes each time.
Power cuts and building maintenance
Reptiles tolerate a heating outage better than fish tolerate a filter outage — a healthy adult in a warm room is fine for many hours. The risk case is a young animal, a species with a high minimum, or an outage in winter with the room already cool. Know in advance where your torch, spare thermometer and a couple of instant heat packs are. The broader household plan for outages, including what to do about tanks in the same flat, is in the UAE power cut emergency plan.
Dust, and the thing on top of your tube
Fine dust is a constant here, and a film of it on a UVB tube or reflector meaningfully cuts output — as does the mineral haze that builds on the inside of a lamp guard in a humid enclosure. Wipe the tube, the reflector and the mesh directly under it every month with a dry cloth. It costs nothing and recovers output you already paid for.
A mounting and wiring checklist
- Every heat source on a thermostat of the correct type. No exceptions, no "it's only 25 watts."
- UVB tube on a plain timer, matched to a sensible photoperiod — 12 hours is a reasonable default for most species, adjusted seasonally if you want to be precise.
- Ceramic sockets for anything producing heat. Plastic sockets fail.
- Lamp guards on anything the animal can physically reach. Contact burns from a CHE or halogen are severe and immediate.
- Fixtures mechanically secured — screwed or clamped to the enclosure or a stand, not resting on a mesh lid held by gravity. A dome lamp that falls into a bioactive substrate is a fire.
- Cables run so the animal cannot pull the probe or the fixture, and so that nothing crosses a water dish or a misting zone.
- An independent digital thermometer at the basking site and a second at the cool end, plus an infrared gun for surface checks.
- Install dates written on every bulb.
The mistakes that come up again and again
Buying a kit and trusting it. Bundled kits are assembled to a price point. The commonest shortfalls are a compact UVB coil where a tube is needed, no thermostat at all, and a bulb wattage chosen for a generic enclosure rather than yours.
Measuring air instead of surface. The air 10 cm above a basking rock and the rock itself can differ by 8 °C or more. The animal lies on the rock.
Heating the whole box. If the cool end is not genuinely cool, there is no gradient, and the animal has no way to regulate. In a small enclosure this is very easy to do by accident.
Treating UVB as a one-time purchase. It is a consumable with an expiry date, like a water filter cartridge.
Letting the animal climb into the lamp. Décor gets rearranged; the minimum safe distance does not move with it. Re-check clearance every time you redecorate.
Assuming supplements replace UVB. Dietary D3 helps and is standard practice for some species, but for a diurnal basking reptile it is a supplement to UVB, not a substitute for it.
The bottom line
Split the two jobs. Buy a UVB tube sized to your species and mounted at a distance the manufacturer specifies, on a timer, replaced on a calendar rather than when it stops looking bright. Buy a heat source appropriate to the time of day it runs, put it at one end only, and put every watt of it behind a thermostat of the matching type with the probe secured where it reflects what the animal experiences. Then verify with an independent thermometer, and re-verify whenever your household AC habits change — which in this country means at least twice a year.
Done that way, the running cost is small and the failure modes mostly disappear. If you are also budgeting for the aquarium side of the household, the same wattage-times-hours arithmetic applies there too, and we worked it through in detail in what a fish tank actually costs per month in Dubai.