Understanding lighting is one of the most important and most confusing aspects of reptile keeping.  Reptile lighting can be broken down into three categories:  UVA, UVB, and Visible Light.  This training course is designed to help you understand these categories, the importance of each category, and how reptile keepers can provide each for their pets.

Each lighting category provides different benefits for reptiles, but all are important for their health and well-being.

First of all, it is important to differentiate between lighting and heating.  Although “light bulbs” can be used as heat sources, this will not be the focus of this course.  Heating elements, including heat lamps, will be covered in the “Heating” Training Course.

Reptile Lighting Terms

Full Spectrum: The term “Full Spectrum” is used rather loosely but can usually be expected to mean that the lamp produces close to the full visible spectrum of visible light.  These lamps often operate in the range of 400 – 800 nanometers and simulate the optical brilliance of outdoor light at noontime.  Often incandescent household lighting products are sold as “Full Spectrum” even though they do not provide UVB or other essential lighting components.

True Full Spectrum:  This is a term commonly used to discuss lamps that produce the full visible spectrum as well as UVA and UVB.  When in doubt, check manufacturers packaging to determine if lamps do indeed provide UVA and UVB.

UVA (Ultraviolet A): The wavelengths of energy within the electromagnetic spectrum between 315 and 400 nanometers.  The visual spectrum of some animals extends into the UVA range. [

UVB (Ultraviolet B): The wavelengths of energy within the electromagnetic spectrum between 280 and 315 nanometers.  Wavelengths in this range contribute greatest to the biosynthesis of vitamin D in animals.  Wavelengths below 290 are dangerous and are filtered by the earth’s atmosphere.  These wavelengths are considered non-terrestrial UVB as they do not reach the earth’s surface.

UVI (UV Index): A unitless index that was created to measure the intensity of ultraviolet radiation from sunlight and is based on the sun’s potential to cause sunburn.

Ferguson Zones: Four Zones based on the UV Index associated with the photoregulatory behavior of reptiles.

Kelvin Rating (Color Temperature):  Color Temperatures is a measure of a light’s color and is measured in degrees Kelvin.

5.0,  10.0, etc…: Many fluorescent and compact fluorescent UVB lamps are sold as 5.0, 10.0 and the such.  This number describes the percentage of total energy output that is within the UVB range.  For example, 5% of the total energy output from a 5.0 lamp is UVB.  Since this number is based on the TOTAL energy output, the UVB output from a 5.0, 54 watt High Output T5, is going to be greater than the UVB output from a 10.0 26 watt compact fluorescent.

Ambient Lighting: Ambient lighting is incidental light that illuminates living spaces. For Example, overhead lights in a classroom that a class pet lives in or skylights in a living room where a pet may be housed.

Incandescent Lamp: An Incandescent lamp or incandescent light bulb is an electric light with a wire filament that is heated to such a high temperature that it glows with visible light.  Many reptile heat lamps utilize tungsten filament incandescent technology.  These lamps are not capable of emitting UVB.

Fluorescent Lamp: A Fluorescent Lamp or fluorescent tube is a low pressure mercury-vapor gas discharge lamp that uses fluorescence to produce visible light.  An electric current in the gas excites mercury vapor which produces short-wave ultraviolet light that then causes a phosphor coating on the inside of the lamp to glow.  Some of these lamps can be made to produce UVA and UVB.  There is very little heat emitted by this type of lighting. Fluorescent lamps are available in a variety of different sizes and styles and must be used in an appropriate fixture with a ballast.  T8, T12, and T5s are all examples of fluorescent lamps.  Because they contain trace amounts of mercury, they are classified as household hazardous waste and should be disposed of accordingly. As long as the lamp remains intact (glass is not broken) the mercury will remain inside the lamp and does not pose any threats.

Compact Fluorescent: A Compact Fluorescent Lamp (CFL) also called compact fluorescent light, energy-saving light, and compact fluorescent tube, is a fluorscent lamp designed to replace an incandescent light bulb.  These lamps use a tube which is curved or folded to fit into the space of an incandescent bulb, and a compact electronic ballast in the base of the lamp.  Like fluorescent lamps, these lamps contain trace amounts of mercury and should be disposed of accordingly.

LED: LED stands for Light Emitting Diode and is a new, extremely efficient form of lighting.  Currently, these lamps are not reliably used to emit UVA or UVB, but can produce many colors within the visible spectrum and are excellent for visible terrarium and aquarium lighting.

Self Ballasted Mercury Vapor (MVB): A mercury vapor lamp is a gas discharge lamp that uses an electric arc through vaporized mercury to produce light.  The arc discharge is generally confined to a small fused quartz arc tube mounted within a larger glass bulb.  Specialized MVBs have been designed to produce UVB as well as UVA, visible light, and heat for reptiles.

Metal Halide: A metal-halide lamp is an electrical lamp that produces light by an electric arc through a gaseous mixture of vaporized mercury and metal halides (compounds of metals with bromine or iodine). It is a type of high-intensity discharge (HID) gas discharge lamp.  These lamps are not self ballasted and must be used in an appropriate fixture with a ballast. Metal Halides are capable of producing UVB, UVA, Visible light, and Heat.


What is UVA?

UVA is part of the sun’s natural spectrum that sits right between Visible Light and UVB.

While people cannot see UVA, most reptiles are equipped with a fourth cone in the retina that allows them to sense this portion of light. UVA is essentially another color that these animals can see that has reactions with the environment, providing important visual cues pertaining to food and other animals – specifically other animals of the same species.

These cues help reptiles make decisions about eating and breeding, so it is a very important part of the spectrum for them. Without exposure to UVA lighting, reptiles are essentially colorblind and may react poorly when presented with food and/or mates. A habitat that provides this component is likely to increase feeding responses, reproductive behaviors and general well-being of pet reptiles.

How can you provide UVA to pet Reptiles?

Natural sunlight is one way to provide UVA, so animals that are housed outdoors will have all they need. However, many species cannot be kept outdoors and many places are not suitable for keeping pet reptiles in outdoor habitats. For pets that are housed inside, there are many different options for providing UVA. First of all, any UVB source (Reptisun & Powersun) will also provide UVA, but there are a few other lamps that can provide additional UVA: Basking Spot Lamp, Repti Halogen, Daylight Blue, and ReptiTuff Splashproof Halogen lamp.





How Long Should UVA be left on an animal?

In nature, reptiles would be exposed to UVA whenever the sun is up, so our pets habitats should mimic that cycle. UVA, UVB, and visible light should all be provided during the same 10 – 14 hours per day (during day time). This is called a Photoperiod (we will go into further detail on that in another lesson). There is no need to try to provide UVA at night or any time that daylights are off.

Facts to Remember:

  • UVA is part of the sun’s natural spectrum that reptiles and amphibians can see.
  • UVA aids these animals in mate selection, species recognition and food recognition.
  • Without UVA, reptiles and amphibians are essentially colorblind.
  • Proper exposure to UVA can encourage natural feeding and breeding responses while promoting well being and health.


What is UVB?

UVB is part of the natural spectrum produced by the sun.

Why do animals need UVB? 

Many animals (most reptiles and birds) are able to utilize UVB to manufacture their own Vitamin D3. While some species are able to get Vitamin D3 from their diet (like snakes that eat whole prey items such as mice), most insectivores and herbivores must make D3 of their own.

Vitamin D3 is responsible for calcium metabolism, and if there is not enough circulating vitamin D3 in the blood, animals are not able to use the calcium in their gut that comes from their food. Dietary calcium would then pass through the gut unused, and animals would be forced to take it from their bones, ultimately leading to a form of Metabolic Bone Disease (MBD).  MBD causes reptiles’ bones to become soft, resulting in severe deformities of the spine, broken legs and soft jaws. In severe cases, the internal organs can calcify and become hard—which can ultimately result in death. In addition to being a major component of bones and eggshells, calcium is involved in countless biological processes at the cellular level, including cell communication, muscle contractions and other functions that are essential to life.

In the early days of keeping reptiles, little was known about the specialized lighting requirements of the majority of reptile species. During this time, reptiles housed indoors were not exposed to UVB, and as a result, would often develop Metabolic Bone Disease (MBD).

For a more in-depth information about UVB and reptile lighting, read this article:

How do animals get UVB?

In outdoor habitats, animals receive their UVB from the sun. Indoors, however, a UVB source must be provided. Contrary to popular belief, placing a pet’s habitat near a window will not suffice as household glass and plastics effectively filter out UVB. In addition, placing a glass terrarium in direct sunlight (including sunlight coming through a window) can be very dangerous. Glass terrariums can act as a greenhouse and trap heat, allowing the habitat to get far too hot to be safe for pets. NEVER PLACE A GLASS TERRARIUM IN DIRECT SUNLIGHT!

Facts to Remember:

  • While UVB is important, more is not always better!
  • Always follow manufacturer’s guidelines.
  • Use UVB lamps for 10-14 hours a day.
  • Some reptiles are thought to not need UVB, but research has shown that most will benefit from some (even low level) exposure.
  • Replace UVB lamps at least once a year.

-Record Date of First Use on bulb,  and

-Use “UVB Reminder” at


There are many different options available for reptile keepers to provide UVB to their animals. Over the years, the options have become so numerous and variable, some may find it difficult to decide which product is right for them.

The factors in choosing correct UVB lighting include the type of animal being kept, the size of the enclosure, and the distance from the light source to the basking area.

Here is a chart that can help you select the best UVB lamp for your pet.  For reference, this chart can be found in Zoo Med Catalogs, at, and in various other educational materials from Zoo Med Labs.

UVB Options:

[UVB Product lineup photo]

Reptisun Mini Compact Fluorescents – 13 Watts

These are our smallest UVB lamps. They are good for small habitats and have an active UVB range of 7″ for the 5.0 lamp and 8″ for the 10.0 lamp. These bulbs can be used in our Mini Deep Dome, clamp lamps, and Naturalistic Terrarium Hoods.

Reptisun Compact Fluorescents – 26 Watts

With a standard threaded base, these lamps are easy to use in our Deep Dome lamp fixtures and Naturalistic Terrarium Hoods. The UVB travels to a distance of 10″ with the Reptisun 5.0 lamp, and 12″ with the Reptisun 10.0 lamp. These lamps are used in many of our kits as they provide the correct UVB to the types of animals designated for our kits. If someone should choose to house a different species in the kit than what is recommended, the included bulb may no longer be sufficient. Linear Fluorescent lamps are available in many different sizes and outputs. T8 lamps are one inch in diameter and are available in 5.0 and 10.0 varieties. These lamps must be used in a T8 fixture that supplies the correct amount of power.

High Output T5 Lamps, or HOT5, produce UVB that travels a greater distance. These lamps are great for use in larger habitats and for basking species that have a high UVB requirement. HOT5 lamps must be used in High Output T5 fixtures. Note that not all T5’s are HO; there are also Normal Output (NO) and Very High Output (VHO) varieties. Be sure the proper fixture and ballast are being used.

PowerSun® UV

The PowerSun® UV is a Self Ballasted Mercury Vapor bulb that provides Visible light, UVA, UVB and Heat. This bulb fits into a standard ceramic socket and does not require a ballast. The 160 Watt projects UVB up to several feet from the lamps surface, and is ideal for large terrariums or bird aviaries. The PowerSun® UV is a great choice for basking species and a simple way to provide for reptiles’ daytime lighting needs with a single lamp. These bulbs are available in 100 watt and 160 watt varieties.

PowerSun® HID

The PowerSun® High Intensity Discharge (H.I.D.) is a Metal Halide lamp which emits UVA, UVB, and heat all in one lamp! This High Output UVB lamp is perfect for large habitats. The proprietary Zoo Med lamp construction creates a true flood-lamp effect, eliminating dangerous UV “hot-spots” common to other metal halide reptile lamps. This is a 70 watt lamp and must be used in the 70 watt metal halide ballast. (See PowerSun® HID Lamp Fixture.)


UVB can be tested in a few different ways.  In the past, use of a UVB radiometer allowed us to measure the number of microwatts per square centimeter of UVB were available in a given area.  One of the problems with this method was that the number that was read from an artificial UVB source could not be compared to that of the sun.  The portion of the light that was measured was too broad and because insufficient research had been done on how many microwatts each animal needed, the number was not terribly useful in determining the ability of animals to produce vitamin D3 with exposure to the light.

Recently, a UV Index Radiometer has been the ideal method of measuring UVB.

Zoo Med’s New Digital UV Index Radiometer to determine if UVB lamps are producing safe and effective levels of UVB. This meter’s response curve is weighted to match the Vitamin D action spectrum to help ensure that pet reptiles are receiving proper and adequate exposure to UVB to help prevent and reverse Metabolic Bone Disease. This meter is easy to use and includes a quick reference scale to help determine the correct levels of UVB for various reptile species.

Additional Information:

  • Measures UVB and provides readings based on the UV Index.
  • Quick reference scale on meter helps determine correct UVI level for various species
  • Meter’s response curve is weighted to match the Vitamin D action spectrum.
  • Determine if lamps are producing safe and effective levels of UVB.


Visible light refers to the light that humans can see. Visible light plays an important role in the health and well-being of reptiles in a few different ways. As discussed in the UVA course, reptiles have excellent color vision. Visible light is an essential component of a reptile habitat to ensure that these animals are seeing correctly.

There are several different ways of providing visible light. The ambient lighting from the room will influence terrarium lighting, but ideally, lighting specifically for the terrarium will provide the visible light for pet reptiles. Both the terrariums above have UVB and Heat Lamps, however the one on the right has LED to add visible lighting.

Many Daytime Heating Lamps and UVB Lamps will provide sufficient visible light, but there are some options to increase the available visible light and allow you, as a keeper, to manipulate Photoperiods, which will be discussed in the next Unit.

LED lighting is very energy efficient and is able to add a lot of visible light to a reptile terrarium without significantly increasing the temperature or using much electricity. This can be especially helpful for animals that appreciate lower temperatures, such as New Caledonian and Mountain species.

Many live terrarium plants have a high requirement for visible light in order to thrive. Live plants can be beneficial as well as beautiful in many different habitats. LEDs are a great solution for providing the light required to keep many of these tropical and desert plants alive indoors.


What is a Photoperiod?

A Photoperiod is the amount of time each day that a plant or animal is exposed to light. In nature, the sun provides a natural photoperiod each day. This time is different in different parts of the world and different times of the year.

Why is it Important?

There is a lot of information that reptiles can get from the light around them, such as the time of day (morning, afternoon, dusk…) and time of year (season). With this information, animals can decide when it is time to hunt, eat, bask, breed, nest, hibernate (brumate) and more. These daily and yearly rhythms are an essential part of a reptile’s life. Even nocturnal species are able to monitor these lighting cycles and adjust their activities accordingly. Adjusting the daytime period can help bring about behavioral changes and may be necessary to induce breeding and other behaviors. In nature, animals are subject to varying daytime periods throughout the year. To best simulate natural conditions, create a shorter daytime period in the winter and a longer daytime period in the summer.

How to provide a Photoperiod

Providing a Photoperiod or Daylight cycle is a very important component of reptile keeping, and can easily be done by turning daylight terrarium lamps on and off. Many different timers are available to help automate terrarium lights and provide a regular photoperiod for your pets.