Reptile Lighting: UVB, Basking, and Heat Setup

Master reptile lighting with this guide to UVB bulbs, basking lamps, and heat sources. Learn what your species needs and how to avoid common lighting mistakes.

8 min read

Reptile Lighting Is Where Most Keepers Get It Wrong

If there's one area of reptile care that generates the most confusion, it's lighting. And honestly, I understand why. Walk into any pet store and you'll find an entire wall of bulbs: UVB, UVA, basking, infrared, ceramic, mercury vapor, compact, linear, coil, and about fifteen different wattages of each. The packaging is covered in vague claims and percentages that don't mean much unless you already understand the science behind them.

I spent my first year keeping reptiles completely confused about lighting. I had a coil UVB bulb sitting on top of a mesh screen, pointed in the general direction of my bearded dragon's basking spot, and I genuinely thought I was doing it right. A vet visit for early-stage metabolic bone disease taught me otherwise. That was the wake-up call that sent me down the rabbit hole of actually understanding how reptile lighting works.

So let's clear up the confusion. This guide covers what UVB actually does, how basking lights work, the different heat sources available, and how to set it all up correctly for your specific situation.

Understanding the Types of Light and Heat

Sunlight contains several types of radiation that reptiles use. In captivity, we need to replicate the most important ones.

UVA (Ultraviolet A, 315-400nm)

UVA light is visible to reptiles but not to humans. It affects how they perceive their environment, influences color perception, appetite, and natural behavior. Most reptile bulbs that produce UVB also produce UVA, so you generally don't need a separate UVA source. Standard daylight bulbs also produce some UVA.

UVB (Ultraviolet B, 280-315nm)

This is the critical one. UVB radiation enables reptiles to synthesize vitamin D3 in their skin, which is essential for absorbing calcium from their diet. Without adequate D3, calcium can't be properly metabolized, and the result is metabolic bone disease (MBD), a progressive condition that softens bones, causes deformities, and can be fatal.

Not all reptiles need the same amount of UVB. Species from open, sunny habitats (bearded dragons, uromastyx) need high-output UVB. Species from shaded forests or that are primarily nocturnal/crepuscular (crested geckos, leopard geckos) need much lower levels. And some species, particularly snakes that are primarily nocturnal, may get adequate D3 through dietary supplementation alone, though providing low-level UVB is increasingly recommended as best practice.

Infrared Radiation (Heat)

Heat from the sun comes primarily in the form of infrared radiation. There are three types that matter:

Infrared-A (IR-A): Penetrates deep into tissue and warms from within. Produced by the sun and by halogen/incandescent bulbs.
Infrared-B (IR-B): Penetrates moderately and contributes to surface warming. Produced by deep heat projectors and some halogen bulbs.
Infrared-C (IR-C): Heats the air and surfaces. Produced by ceramic heat emitters. Doesn't penetrate tissue effectively.

Why does this matter? Because IR-A, the type produced by halogen basking bulbs, most closely replicates how the sun actually warms a reptile. A basking spot heated by a halogen bulb warms the animal's body more effectively than the same temperature produced by a ceramic heat emitter. Think of it like the difference between standing in warm sunshine versus standing in a warm room. The air temperature might be the same, but the sunshine feels different because it's warming you directly.

UVB Bulb Types: Which One Do You Actually Need?

Linear Fluorescent Tubes (T5 and T8)

These are the gold standard for UVB in reptile keeping. They produce consistent, even UVB coverage across their entire length, which means your reptile gets reliable exposure across a meaningful portion of the enclosure.

T5 HO (High Output) bulbs are the current best choice. They're more powerful than T8 tubes, can be mounted further from the basking spot, and their UVB output degrades more slowly. A T5 HO tube mounted inside the enclosure or on top of a mesh screen can effectively illuminate enclosures up to 18-24 inches tall, depending on the bulb strength and screen type.

T8 tubes are lower output and need to be mounted closer to the basking spot. They're adequate for shallow enclosures but have been largely superseded by T5 HO technology.

My recommendation for most setups: get a T5 HO fixture and the appropriate UVB tube for your species. Arcadia and Zoo Med are the two most trusted brands.

Compact/Coil UVB Bulbs

These screw into a standard dome lamp fixture and seem convenient. The problem is that they produce UVB in a focused cone rather than a broad, even spread. This means the UVB coverage area is very small, maybe 6-8 inches in diameter, and your reptile has to be positioned directly under it to get adequate exposure. The edges of the cone can also have uneven intensity.

I don't recommend compact UVB bulbs for primary UVB provision. If you absolutely cannot fit a linear tube, a compact can work as a supplement, but it's a compromise.

Mercury Vapor Bulbs (MVBs)

Mercury vapor bulbs produce UVB, UVA, visible light, and heat all from a single bulb. They're powerful and can work well in large enclosures where you need a strong UVB source at a distance. The downsides: they can't be dimmed, they run hot, and they're not suitable for small enclosures because you can't position them close enough without overexposing the animal to UVB.

MVBs work best in large bearded dragon or iguana enclosures. For most standard setups, a separate UVB tube plus a separate basking lamp gives you more control.

Basking Lights: Creating the Sun Spot

The basking spot is where your reptile goes to heat up its core body temperature for digestion, immune function, and activity. Think of it as their personal sun.

What to Use

Halogen flood bulbs are the best basking heat source currently available. They produce a spectrum that includes visible light and infrared-A radiation, which penetrates tissue and warms the animal efficiently, just like actual sunlight. A standard PAR38 halogen flood bulb from any hardware store works perfectly. You don't need a bulb marketed specifically for reptiles.

Typical wattages range from 50W to 150W depending on the enclosure size and target temperature. Mount the bulb in a ceramic-rated dome fixture and connect it to a dimming thermostat for precise temperature control. The thermostat probe goes on the basking surface, where the animal actually sits.

Standard incandescent bulbs also produce IR-A and work as basking lights, but they're being phased out in many markets. If you can find them, they work fine.

What Not to Use for Basking

Red or blue "heat" bulbs: Despite what the packaging says, these are not invisible to reptiles. The colored light disrupts their day/night cycle and can cause stress. There's no good reason to use them.

Ceramic heat emitters for basking: CHEs produce IR-C, which heats the air but doesn't warm the animal as effectively as a halogen bulb producing the same surface temperature. CHEs are better suited for raising ambient temperatures or providing nighttime heat.

Nighttime Heating

Many keepers worry about nighttime temperatures, but most species tolerate a natural nighttime drop just fine. In the wild, temperatures drop when the sun goes down, and reptiles have evolved to handle that.

General rule: if your room doesn't drop below 65 degrees Fahrenheit at night, most common pet reptiles don't need additional nighttime heat. If your home does get colder than that, use a ceramic heat emitter or deep heat projector connected to a thermostat. These produce heat without light, preserving the dark period your reptile needs for normal sleep.

Never use a regular light bulb for nighttime heat. The light disrupts the photoperiod and prevents restful sleep, which impacts appetite, behavior, and long-term health.

Setting Up Your Lighting: Practical Steps

Here's how I set up lighting in a standard terrestrial reptile enclosure (like for a bearded dragon or blue-tongued skink):

Position the UVB tube to cover roughly one-half to two-thirds of the enclosure length, starting from the basking end. This creates a UVB gradient: highest exposure at the basking spot, decreasing toward the cool end. The animal can self-regulate exposure by moving between zones.
Mount the basking lamp at one end, directly above the basking spot. Use a dimming thermostat with the probe on the basking surface to maintain the correct temperature for your species.
Verify distances. UVB intensity depends heavily on distance. Check the manufacturer's recommendations for your specific bulb. For a typical T5 HO 12% tube mounted on a mesh screen, the basking spot should be roughly 12-15 inches below the bulb. Mesh screens filter 30-50% of UVB, so account for that.
Set up timers. Both the UVB and basking lamp should be on timers providing 12-14 hours of light in summer, 10-12 in winter. Consistency matters. Don't manually toggle lights on and off at random times.
Confirm with a temperature gun or probe thermometer. Measure the actual basking surface temperature, not the air temperature. An infrared temperature gun is one of the best $15-20 investments in reptile keeping.

UVB Requirements by Common Species

Here's a quick reference for some of the most popular pet reptiles:

Bearded dragons: High UVB (T5 HO 12-14%). Ferguson Zone 3-4. Basking temp 100-110 degrees F.
Blue-tongued skinks: Moderate-high UVB (T5 HO 10-12%). Ferguson Zone 3. Basking temp 100-105 degrees F.
Leopard geckos: Low UVB (T5 HO 5-7% or ShadeDweller). Ferguson Zone 1-2. Belly heat 88-92 degrees F.
Crested geckos: Low UVB (T5 HO 5-7%). Ferguson Zone 1-2. No supplemental heat in most homes.
Ball pythons: Low UVB is beneficial but optional (T5 HO 5-7%). Many keepers supplement D3 through diet. Basking temp 88-92 degrees F.
Corn snakes: Low UVB optional. Warm side 82-86 degrees F.
Russian tortoises: High UVB (T5 HO 12-14%). Ferguson Zone 3-4. Basking temp 95-100 degrees F.

How Often to Replace Bulbs

This is the part that catches people off guard. UVB bulbs degrade over time, even though they still produce visible light. A bulb that looks perfectly bright can be putting out negligible UVB after several months of use.

T5 HO tubes: Replace every 12 months.
T8 tubes: Replace every 6 months.
Compact/coil bulbs: Replace every 6 months.
Mercury vapor bulbs: Replace every 6-12 months depending on usage hours.

Write the installation date on the bulb with a marker. It's impossible to remember otherwise, and your reptile's bone health depends on it. If you want to verify output precisely, a Solarmeter 6.5 UV meter will tell you exactly how much UVB your bulb is producing, though at around $250, it's more of an investment for serious keepers or breeders.

Common Lighting Mistakes

After years in online reptile communities, these are the most frequent lighting errors I see:

Using only a basking lamp with no UVB. Heat and UVB are separate needs. A basking lamp does not produce UVB. Your reptile can be perfectly warm and still developing metabolic bone disease.
Mounting UVB outside a mesh screen without accounting for filtering. Dense aluminum mesh can block 50% or more of UVB. Either mount the bulb inside the enclosure with a guard, or use a screen with wider mesh and adjust the bulb distance accordingly.
Never replacing UVB bulbs. I've talked to keepers using the same UVB tube for 3+ years. At that point, it's producing basically zero UVB. Set a reminder on your phone.
Placing UVB at the wrong distance. Too far away and the animal gets insufficient exposure. Too close and you risk photokeratoconjunctivitis (basically a sunburn of the eyes). Follow the manufacturer's distance guidelines.
Leaving lights on 24/7. Reptiles need a dark period. Constant light causes chronic stress, disrupts hormones, and suppresses appetite. Use a timer.
Using colored bulbs for daytime or nighttime. Red and blue bulbs are visible to reptiles and disrupt their natural light cycle. Use white/daylight bulbs during the day and lightless heat sources at night.

Bringing It All Together

Reptile lighting doesn't have to be overwhelming once you understand the basic framework. Your animal needs three things from its lighting setup: appropriate UVB for vitamin D3 synthesis, a basking spot with adequate heat for thermoregulation, and a consistent day/night cycle controlled by timers.

Get a T5 HO UVB tube in the right strength for your species, a halogen flood bulb on a dimming thermostat for basking, and lightless heat for nighttime if needed. Replace UVB bulbs on schedule. Verify temperatures with an actual thermometer, not guesswork.

Once it's dialed in, the maintenance is minimal: replace bulbs on schedule, check temperatures periodically, and make sure everything is running on timers. Your reptile's health, behavior, and coloration will tell you when the lighting is right. Active, eating well, shedding cleanly, and displaying vibrant colors? You nailed it.

Frequently Asked Questions

Do all reptiles need UVB lighting?

Not all reptiles strictly require UVB, but most benefit from it. Diurnal species like bearded dragons and tortoises absolutely need UVB to prevent metabolic bone disease. Crepuscular species like leopard geckos benefit from low-level UVB. Nocturnal snakes can often get adequate D3 from dietary supplementation, but providing low UVB is increasingly considered best practice for all species.

Can I use a regular household light bulb for my reptile?

Regular household incandescent or halogen bulbs work perfectly well as basking heat sources, and they're often cheaper than bulbs marketed specifically for reptiles. However, they do not produce UVB, so you'll still need a separate UVB tube. LED bulbs don't produce meaningful heat or UVB, so they're not useful for reptile heating or UV needs.

How do I know if my UVB bulb needs replacing?

Unfortunately, you can't tell by looking at it, as the visible light output remains long after UVB output degrades. The most reliable method is to track the installation date and replace on schedule: every 12 months for T5 HO tubes, every 6 months for T8 and compact bulbs. For precise measurement, a Solarmeter 6.5 UV index meter can directly measure UVB output.

Is it safe to mount a UVB bulb inside the enclosure?

Yes, and in many cases it's preferable because it eliminates UVB loss from screen filtering. Use a bulb guard or wire cage around the fixture to prevent your reptile from direct contact with the bulb, which could cause burns. Ensure the mounting is secure and all electrical components are safe from moisture, especially in humid tropical enclosures.