Reptile UVB Lighting

Did you know that reptiles can see the UV (ultraviolet) spectrum of sunlight? Reptiles, and other vertebrates, have evolved to use the sun’s rays to help with the production of vitamin D3, a crucial nutrient that aids in more than just calcium absorption. Along with providing a seasonal photo-period, sunlight also contains UV wavelengths that promote natural behaviors. However, most reptiles are kept indoors, and even a sunny window doesn’t provide the right wavelengths of unfiltered daylight. We don’t know exactly how this affects reptiles, but it’s likely affecting their color vision in some way, as they see more colors (wavelengths) than humans. Providing lighting in as full a spectrum as possible, including UVA and UVB, would be ideal.

Zookeepers have been using “artificial” sunlight in the form of UV-producing light bulbs. However, over the years they’ve found that there are multiple forms of UV – some beneficial, and some dangerous. Just as humans can be sunburned, reptiles can have tissue damage on their skin and their eyes as they continue to bask in highly-concentrated UV rays. The forms of UV we want to see produced in our bulbs are UVB (for vitamin D production) and UVA. Old style bulbs only produced some UVA, and were ineffective at producing vitamin D3. UVC is harmful, it is short-wavelength radiation and in nature is blocked almost entirely by the ozone layer and oxygen in the atmosphere. However, due to its damaging effects it makes a good germicide and can help rid the air of impurities.

Do Reptiles Need UVB?

Lighting needs depend on the species. Most reptiles can survive and even thrive without a UVB source, as long as they have been fed a diet supplemented with calcium and Vitamin D3. However, studies and anecdotal evidence suggest that natural sunlight or an artificial equivalent can improve the health and encourage natural behaviors in many species of reptiles. Even nocturnal geckos or shade-dwelling tortoises and lizards can benefit from UVB. If you do not have the climate or the means to house your sun-loving reptiles outside, you’ll want to consider the use of UVB bulbs.

Even the best UV bulbs aren’t perfect; it’s hard to exactly match the output of the sun’s rays consistently and without spikes in particular frequencies. Sometimes a manufacturing error can wreak havoc with the UV spectrum they output. These can generate UVC as well as abnormally short-wave versions of UVB and UVA that can be damaging to our pets. You may have heard of the compact “coil” UVB bulbs being very bad for reptiles. Luckily, this is no longer the case for the name brands, but there are some cheaper imports that still can cause problems. There are many great resources for understanding technical details and specifications of these bulbs. Check out for some great information on why UVB is important for reptiles, how it is generated in a light bulb and how it can be measured and monitored for safety.

To find out what level of UVB your reptile needs, check out the Ferguson Zone species guide from ZooMed. For example, nocturnal animals like crested geckos would be Zone 1, while diurnal basking lizards like Uromastyx would be Zone 4. Each species has their own need, and you’ll need to know the minimum and maximum distance the bulbs can be placed from your pet.

We’ll give some details about the use of tube lights, compact fluorescents, and Mercury Vapor bulbs. We’ll cover the major brands available in the US that have been measured with a quality UV meter (such as Solarmeter from Solartech) and examined for use with reptiles by the good folks at UVGuide UK and the UVB Meter Owners Yahoo! Group (multiple posts, files, and other sources). We’ve relied heavily on this research to create this guide, and if new data is released we will keep this page updated.

Data current as of late 2014.

Note: Using a radiometer that can measure UV light is the best way to monitor the output and decay of your reptile lights. Readings will vary by device type and the calculations or ratios of the measurements. Most enthusiasts use a Solarmeter by SolartTech or a ZooMed Digital UVB Radiometer. Here are detailed instructions on how to use these devices, again courtesy of UV Guide UK.

General Light & UV Considerations

You need to be careful when providing UV rays and heat to your animal, as both under supplying and over supplying will cause harm, either immediately or over time. It is unlikely that one single bulb will serve all your heating and lighting needs, so be sure you are taking into consideration the needs of your particular species. Artificial lighting still does not replace the full spectrum of sunlight that reptiles see and respond to.

Be sure you are providing a temperature (and UV) gradient for your animals to regulate according to their needs. UVB rays work in conjunction with heat for proper Vitamin D3 conversion, so ensure proper heating and UV exposure evenly over the entire body of the reptile in the basking zone. This keeps the reptile from over-basking while trying to get the right level of heat to accompany the UV rays. This can not only expose them to too much radiation, but also interfere with feeding and sleeping routines.

Visible light to humans is usually within the UVA range, and many UVB-specific bulbs do not provide the full spectrum of color, which can interfere with natural behaviors. You will need another light source, whether ambient room lighting from a window, or another bulb (or more) for the enclosure. Most fluorescent bulbs do not give off much UVA, so look for incandescent lighting to supplement the red & yellow spectra of light.

  • Not all brands are equal
  • Price often indicates quality
  • UVB bulbs all degrade (decay) over time
  • Most UVB bulbs should be replaced every 6-12 months (use a meter
    Bulb UV level labeling is not always accurate – some bulbs for tropical species emit more UVB with less decay
  • Use the appropriate level of UV for each species (based on meter readings not labels)
  • Most glass or plastic will filter out UVB rays
  • Metal reflectors can greatly enhance the UV output – great for desert species but use with caution
  • No bulb should be closer than 6 inches; 12 is the standard minimum for tube bulbs but some require 15+

Safety Concerns

The main risks associated with UV-producing light bulbs are cellular damage to skin (sunburn and related effects) and eyes (photo-kerato conjunctivitis). This occurs when the UV generated is within the damaging, shorter wavelengths, the result of using the wrong type of glass or the wrong of phosphor in the white coating that is supposed to filter out these damaging rays. Manufacturing issues can also be an issue, if the coating is inconsistently applied, there are streaks of uncovered glass or the phosphor is somehow rubbed off during assembly.

Use appropriate supplemental heating and lighting, since many reptiles may be over-exposed to UV while basking as they try to thermoregulate. If the overall light is not bright enough from other light sources, some reptiles remain in hiding and stay dormant during the day, as they would during winter brumation when there is less daylight.

Be sure there adequate retreats or “hides” in the enclosure for your reptile to escape the UV rays during the day. This is especially important for geckos, many of which do not have eyelids. These hides should also provide higher levels of humidity to counter the dehydrating effects of basking lights.

UV Tube Lights

Tube lights generally come in T5 or T8 forms. T5 are smaller in diameter and are generally higher in quantity and efficiency of the light generated. You need to know the type of fixture you are using and match the bulb – or vice versa. T8 is most often available in US pet stores as these are cheaper to produce, but some brands do offer both versions. Hoods for terrariums are usually T8. For the purposes of UVB production, the T5 generally have a higher output but a good T8 bulb will suit most setups.

You also need an appropriate fixture for your enclosure. Most commercial hoods are fine, but are designed to be placed over mesh screen tops which can block some or most of the UVB. It may be better to get a fixture that can be mounted inside the tank instead of one placed on top.

Arcadia makes a wide range of tube lights and excellent fixtures. However, they aren’t commonly available at pet stores, but you can order at Light Your Reptiles
Their D3 & D3+ product lines are some of the best UVB emitters in the US. Remember to choose the appropriate T8 or T5 bulb for your fixture!

ZooMed T8 and T5 Repti-Sun bulbs can be used. However, Exo Terra Repti Glo tube lights have changed their specifications frequently in the past, and no current data is available. However, after rooting around in the UVB Meter Owners Yahoo! Group, the data hasn’t been good with regards to short wavelengths emitted and rapid decay of UVB. So we do not currently recommend them because of the possible health risks of improper wavelengths or insufficient UVB.

Mercury Vapor Bulbs

Since another function of sunlight is heating these “cold blooded” reptiles, some new types of bulbs, called Mercury Vapor bulbs, create both heat (infrared radiation) and UV rays.

Use UVB Mercury Vapor basking lights with caution. They typically have spikes through the UV spectrum; so although not necessarily a health risk, it is not as consistent as other bulbs. Additionally, their wavelengths are typically shorter than sunlight, and that can potentially cause cell damage & photo-kerato-conjunctivitis. Because the need to place them high enough so the UV doesn’t damage the animal, the heat it produces generally dissipates and is often not sufficient to heat the area. This may result in the animal staying under the basking light longer than necessary, exposing them to too much UV, leading to the above issues. The minimum recommended distance is at least 12 inches (30cm) between the bulb and the animal. Many bulbs experience UV decay, which means that the UVB output is reduced after about 10 days of use, effectively requiring a max of 12 inches in order to be effective. Most produce spikes of long-wave UVA and some produce short-wave UVA, but most are low output of this light, which is visible to reptiles.

The Arcadia 160w Basking Light is acceptable at 12 inches, as are Mega Ray at 14 inches (35cm) for 100w and 20 inches (50cm) for 160w. Both have much less decay, although they are still slightly more risky than sunlight if your reptile basks too often directly beneath the bulbs.

ZooMed’s PowerSun 100w has some decay after 10 days, so minimum placement is 12 inches, depending on species. 160w is more intense and is perfect for Uromastyx at 12 inches, farther away for other species. It also produces some continuous spectrum UVA.

Exo Terra’s SolarGlo 125w has a very narrow beam and after decay can create an acceptable basking spot for smaller animals. 160w creates a wider basking spot at 12 inches but but much lower UV Index after a 10-day decay. Not recommended for Uromastyx, but could be used on species with lower UVB needs.

Coil Bulbs

While UVB-producing compact fluorescent coil bulbs have been implicated for problems in the past, most of the name-brands you encounter are safe for your pets. However, depending on your species, they don’t produce nearly enough UVB for diurnal and desert species. They can be a very good choice for nocturnal or tropical species such as chameleons, crested geckos and other New Caledonian geckos. Uromastyx and other desert lizards would require a high number of coil bulbs that would be cost-prohibitive.

The old bulbs from 2006-2009 could still be in circulation. The brands affected were Zilla and Zoo Med, while Exo Terra Repti-Glo 5.0 coil bulbs did not have problems, but the 10.0 came close to the problem wavelengths. People were advised to avoid all coil bulbs during this time.

All of the aforementioned brands now produce safe coil bulbs, but be wary of older products still on the market.

Even today, you may find cheaper and off brand bulbs that are made from the same facilities that produced the faulty bulbs. Either avoid these bulbs or continually monitor their short-wave UV output with a UV-reading radiometer.

Please refer to the UVB Meter Owners Yahoo! Group for details on the bulbs that were tested. Most have files uploaded but you may have to dig for specific models. And if you have a radiometer, they can help you understand the readings for your lamps.

UV & Lighting References

2 thoughts on “Reptile UVB Lighting

  1. I have a question, if a lizard was to be over exposed to their UVB light, what would some side effects be?

    We were having issues with his tank staying warm enough at night we have a fixture that houses both the UVB and the heat lamp together, and for a few days we just left them on to make sure he stayed warm until I got paid and was able to purchase a second house with a night light.

    I just would like to know how to tell if he would be I’ll from overexposure, because I never thought about the fact that his uvb was connected in there until reading this article just now and I feel bad

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