Introduction to this page

There are a number of things that one must learn to truly understand chameleon husbandry. UVB is one of those things which takes a great deal of thought and understanding. The Chameleon Academy was designed for those who have a hunger to know and so this is where we dig deep. Grab a coffee and get comfortable because this will take a bit of time. But by the end you will have a working knowledge of UVB and will be able to set-up a chameleon appropriate cage with many different UVB bulbs.

In this section we will start by understanding why we care about UVB, what it is, how to measure results, and how to set-up a cage with the UVB light of your choice.

The “proper” UVB is not a bulb, but a deliberate UVB exposure map within the cage using an effective bulb, fixture, basking branch, and distances to achieve the goal.

Listen to a Podcast of this page!

UVB Quick Fix

UVB placement for Chameleons

First, let’s start at the end!

Here is the universal formula as to how to set up UVB on your chameleon’s, or really, any reptile’s cage:

First, you determine what your target basking UVB level is.

Second, What is the maximum UVB level that you want your chameleon to be exposed to

Third, How much space do you want to be between those two values? In other words, how much space do you need to work with? Obviously, a baby panther chameleon will not require as much space as an adult Parson’s Chameleon.

And then you pick the UVB bulb that gives you those values across your required amount of space.

This page is designed to give you a firm grasp on UVB basics as they relate to keeping chameleons. If you are looking to hear how to set up your UVB light here is what you are looking for

  1. Get a Reptisun 5.0, Arcadia ProT5 6%, or Leap 5.0 linear T5 High Output UVB bulb in a good single bulb reflector.
  2. Mount the fixture 2-3” above the cage screen top
  3. Position your basking branch 6” below the top of the cage directly under the UVB bulb.
  4. Power your UVB bulb on the same timer as your main lights.

There, that is all you need to know and you can go on to getting together other things. But, if you want to know why you do any of that and what it means, then return back or continue on and I will explain it all. And when I say all, I mean we are starting at ground zero and answering why are we using UVB to being with. But, by the end of this page you will be able to put together a strategic UVB exposure gradient and know how to pick the correct bulb, fixture, and placement to achieve the goal you have set.

So, let’s get on with laying the knowledge foundation

Why is UVB Important?

To start we need to understand what it is we are talking about. UVB stands for UltraViolet B. This is a narrow band of light wavelengths that are part of sunlight. They are powerful rays and just a little higher wavelength and you get into UVC which we use to sterilize equipment and are naturally filtered by our atmosphere. Or else they would kill us. UVB isn’t benign either. It burns our skin, destroys cells, and causes cancer. So, we are talking about a charming group of energies. Because nature has a sense of humor, it made UVB critical to our survival. Don’t you love how this works? Because our skin uses that narrow band within the UVB range to start the process of creating vitamin D3. This process starts in the skin and continues on through the kidney and liver. The final hormone, Vitamin D3, is what our body, and chameleons’ bodies, use to extract calcium from our food. Without vitamin D3, the calcium would just go through the digestive system and be dumped unceremoniously out the back end. Calcium is what we use to grow our bones and make them rigid. This is the skeleton that makes life possible. It also is required for proper organ function so we need that calcium!

I am sure you have heard that we can include vitamin D3 in the diet through our supplementation powders and it has the same effect with calcium. So, why deal with UVB light if it can be dangerous? Great question, and the answer is that vitamin D3 can be overdosed as well. It is a fat soluble vitamin and so excess is stored rather than flushed out like a B vitamin. The body does not have a regulating mechanism for ejecting excess D3 when it comes in through the diet. And if you have too much D3 in your system and you start getting more calcium than you can store in your bones, then the body starts putting calcium in places it shouldn’t be, like on the organs. So, we need to stay away from that. 

On the other hand, the UVB process is highly regulated. The chameleon’s body knows how much vitamin D3 it has in its body and when it has enough, the body stops vitamin D3 production from UVB. UVB light exposure after that is ignored for the purposes of D3 production. So we just have to make sure that the UVB levels that are in the chameleon cage are both safe and effective and we can let the chameleon’s body take care of the rest. You cannot have D3 overdose when using UVB light.

This is why, when we use supplement powders we use plain calcium for everyday feeding, avoid the calcium with D3 supplements, and only use multivitamins with D3 every other week or even just monthly. Ideally, your chameleon is getting the bulk of its vitamin D3 from UVB light exposure under complete regulation by the chameleon’s body. In fact, under a robust UVB system like I described at the beginning of this podcast, you only need to include D3 with the supplement to be with vitamin A. They have some strange relationship that we don’t fully understand, but it is generally accepted that they should be given together. I will full admit that I am just beginning to figure out what their “antagonistic” relationship means to us chameleon people and will happily share once I have gotten to the bottom of it. But I have personally proven that with the UVB set-up described, you need no additional dietary D3 for calcium absorption. I still have a bi-weekly multivitamin on my care summaries, but that is for the vitamin A.

So, now we know what UVB is and why we need it. We now go to how we get UVB. UVB is a component of sunlight and if your Chameleon gets access to unfiltered sunlight you are golden. But for indoors keeping we either need to give D3 through our supplements, and that is how it was done before UVB lights, but we live in an age where our technology has allowed us to have lights that are specifically made to radiate the right UVB wavelengths for vitamin D3 synthesis.

UVB/D3 cycle

UVB Technologies

We get UVB light into our chameleon cages using special lights designed to produce UVB. Remember how I said it could be dangerous? Well, that is a big reason why standard lights do not give off UVB. They are specifically designed to cut off the light spectrum before that. The last thing we need is to get a sunburn after a late night studying for finals!

We, as chameleon keepers, need those wavelengths so we have available to us lights specifically designed for the reptile community that give off the correct UVB wavelengths for vitamin D3 synthesis.

There are a handful of technologies that emit UVB. There are metal halide lights, Mercury vapor lights, fluorescent lights, and now we have LED lights. The most commonly used technology is the fluorescent light and so I will focus on explaining that.

If you have shopped for a UVB light I wouldn’t be surprised of you were shell shocked and confused to the max at all the varieties you have to choose from. Even in just the fluorescent space there are different shapes, different technologies, and different strengths. Triple yikes! 

So, let’s do a mini guide with only the information you really need to know

Shape. Most fluorescent bulbs you see are linear. Meaning they are in a tube and they fit into a long fixture. That is the one we want when we are lighting an adult size chameleon cage. The reason why there can be confusion is that some enterprising investor figured out that if you coiled the bulb up a bunch you could get the power efficiency of fluorescent technology and use it in standard home light sockets. And that was a geniuses idea! They called the CFLs, or Compact Fluorescent Lights. Except they have the characteristic that all those twists and turns end up having the bulb absorb the energy it just radiated on any part of the bulb not facing out. I suppose that is okay for lighting a room, but, when it is made into a UVB bulb it has the effect of severely limiting how far the UVB energy punches into the cage. They definitely have specialty uses in our hobby, but are not serious contenders for general usage.

You will hear a great deal of not so nice things said about CFLs, or compact fluorescent lights, in the chameleon community. Most of those things are not 100% true, but the general feeling of don’t buy them is good advice. It is worth explaining this because when you are sent to go get a UVB light, the CFLs are sitting right next to the linears and you have to know what to get. This is where it gets confusing!

You are looking for the linear tube because that is going to give you the most UVB.

Technology. Now you have all sorts of choices with linear as well. And this is even more tricky than deciding between CFL and linear. There are two technologies available. The older T8 technology and the newer T5 technology. If you have trouble remembering which is the newest just remember that the number is the diameter of the bulb itself. And technology has allowed us to get more light out of smaller bulbs. So,T5, which is a smaller bulb is the latest in technology. Hopefully that made sense! T8s are the larger bulb and are slowly going away, but there are still enough sold in stores and online to make it easy to order wrong. Because you have to pay attention to the number when you order. If any of this didn’t sink in, just remember T5 linear. And that needs to be both for your bulb and your fixture. And I said T5 linear, because all those CFLs use the T5 technology so they might be sold as T5. You have to make sure you get the T5 Linear bulb.

T5 Linear bulbs come in various lengths so you just get the one that is closest to the width of your cage. The length of the bulb will be shorter than the fixture so don’t worry if your cage is 24” wide and the bulb is 22”. The fixture will take up the extra inch on either side.

UVB Strength. You will have to pay attention to the UVB strength of the bulb. Reptisun and Leap use the 5.0 for their lower energy bulb and 10.0 for their higher energy bulb. Arcadia uses 6% for their lower energy bulb, 12% for their higher energy bulb, and, if you really want a tan, they offer a 14%. The advantage of Arcadia and Leap is that they have their own fixtures that are designed to work well with their bulbs. Reptisun has their own fixtures, but I haven’t really had good luck with quality on these. You can, of course, buy your own fixture. Sometimes I use multi bulb agriculture fixtures. But, which ever way you go, make sure the UVB bulb has its own reflector to make sure all the energy goes into the cage.

Length & Fixture. The last parameter to consider when buying a UVB bulb is that you need to get the right size. Linear bulbs will come in different sizes. You want to get the one where the length of the fixture is the closest to the width of your cage. Be aware that the length written on the T5 bulb package will be slightly less than the length of the fixture. The important thing with the fixture is to make sure the technology matches. T5 fixture for a T5 bulb. I love the Arcadia ProT5 series because it is a light bulb and fixture combination that means there is no way to mix it up. Leap only offers T5 lighting so you can’t go wrong there as long as you find the right size for your cage. ZooMed Reptisun has a lot of choices in T5, T8, and CFLs so with that brand make sure you are buying the fixture that goes with the light.

To recap, when ordering a UVB light remember the following

  1. Select a shape. Linear or CFL? Linear is recommended. Select the length that matches your cage width as close as possible.
  2. Select a technology. T8 vs. T5? Select T5
  3. Select a UVB strength. 5.0 vs 10.0 or 6% vs 12%. For the tutorial here I recommend the 5.0/6%
  4. Select a fixture. The Fixture must be for the correct technology and length.

Fluorescent Bulb Shape

CFL styles for chameleon cages

In addition to the common linear bulb shape for fluorescent lights, Compact Fluorescent Lights (CFLs) are available. They are not useful to us in the chameleon community in most cases. But you need to be aware that they exist because they are on the shelf next to the linear bulbs and the description of them on online stores sounds very much like the linear bulbs. So, when ordering or purchasing, make sure the bulb is the shape you want!

Fluorescent Bulb Technology

T8 vs T5 bulbs

Linear fluorescent bulbs come in two technologies, T8 and T5. The T5 is a newer technology and gives more light in a smaller tube. Make sure you know which “T value” you are purchasing and that it matches the fixture. T5 bulbs will not fit in T8 fixtures. This is important to know because if you are buying bulbs and fixtures at a retail location it is common where they will offer T5 bulbs, but only T8 fixtures. The bulb technology must match the fixture technology.

Fluorescent Bulb Strength

UVB bulb strength 5.0 Leap

Each UVB bulb will have a strength rating that indicates how much UVB will be produced. Leap and ZooMed have the 5.0 for their lower level and 10.0 for their higher level. Arcadia uses 6% and 12% with another higher at 14%. The Leap/Reptisun 5.0 is equivalent to the Arcadia 6%. The Leap/Reptisun 10.0 is equivalent to the Arcadia 12%.

Measuring UVB

In the chameleon community we like to measure UVB on the UV Index scale used by the World Health Organization. Their purpose is to determine the likelihood of getting a sunburn. Luckily for us, the same UVB light wavelengths that give us sunburns also is what we use to synthesize vitamin D3. And this is what we care about in the chameleon world! So we have been able to piggyback on their efforts. The standard measurement device is the Solarmeter 6.5 UVB Meter.

Another way to measure the UVB lamp output is in the power that hits a certain area. This is how we measured UVB up until relatively recently. This is important if you decide to do more UVB research because a number of useful studies were done using the units of microwatts per square cm (uw/cm^2). We used to use the Solarmeter 6.2 for this purpose. Unfortunately, there is no conversion formula because the 6.5 and 6.2 measure differently. So if you want to reference the older scientific papers you have to learn to work in uw/cm^2 as well!

But since the WHO cares only about sun burns in humans, we are left to figure out how much UVB chameleons need. This is a huge question because each species could, potentially, require different levels of UVB. Simply because of the filtering aspects of the atmosphere, the UV Index level will rise 2% for each 1000 feet in elevation. Since we have chameleon species that live on the coast and others that live 14,000 feet in the mountains, we have to be prepared to customize our husbandry per species. (Which is hardly a surprise to anyone here!)

For reference, here is a list of some significant UV Index levels

UVI 0 is nighttime. No UVB

UVI 3 is late morning sun in many chameleon habitats. This is actually our preferred basking UV Index. And I will go into that soon.

UVI 6 to 8 is about the most we want to have at the tops of our cages with what we know right now.

UVI 13 is the blasting afternoon sun in many chameleon habitats. We don’t recreating this because they are hiding from this. This is why it is important not to just recreate the levels you read off the internet for Madagascar. They are hiding from these levels!

UVI 18 is what you measure in front of the bulb, even through screen, for the T5 linear 6% or 5.0 that I am telling you to buy. See why we want to get rid of some of that energy before our chameleon can crawl into it?

UVI 43 is the highest UV Index recorded on Earth and it was on a volcano in Bolivia.

UVI 50 is what you can read off of a fresh T5 12% linear Arcadia PRoT5 fixture at the screen top if the bulb is resting on the top of the cage. So, yes, you can with present day technology put UVB levels into your cage which are higher than have been measured on Earth. This is why you do not want to rest a 12% or 10.0 T5 UVB lamp directly on the top of your cage. This was very bad advice floating around social media a few years ago and never made sense even then.

UVI 160 is the highest I have read off of a reptile fluorescent bulb through screen. It was the Exo-Terra 200 26Watt CFL. That is right, the highest power from fluorescent technology in our community comes off of a compact fluorescent light. The reason we don’t use compact. Fluorescent bulbs is not because they can’t create the higher UVB levels, it is that they don’t do it in a useable gradient.

UVB Meters
UV Index

The scale provided by the World Health Organization is designed to warn us when the conditions get dangerous and we have the potential to get sun burned.

UVB light for chameleons

It is useful to know how light comes off of the fluorescent bulbs. Fluorescent bulbs radiate light in all directions and so we need a reflector on the bulb to redirect the light into the cage. As this image shows, the energy into the cage raises dramatically with the reflector. But then we give up some of the gains by going through the filter of the screen top. Most screen cages commercially sold use 70% transmission screen which would filter out 30% of the energy. If you have a finer mesh than standard window screen or a wider mesh, such as if using a bird cage, then your VUB light energy will change from the numbers shown on this page

How much UVB do chameleons need?

The most significant effort to determine how much UVB a reptile needs was carried out by a team of scientists that took into account the environment of certain species of reptiles and put together a set of four zones that they placed species in. These “Ferguson Zones” represented various biotopes. They designated ambient type levels and basking levels. This provided a high level framework to get us started. But there is no way they could have spent the years of experimentation to personalize it to each species. That is where we hobbyists must take this excellent start and use it to further our knowledge. We are the ones that are breeding these species, have access to multiple specimens, and spend every day studying them. It is our turn to do our part. If we wait for scientists to get funding or find time for personal projects we could be waiting a very long time. Let’s not be that patient.

And we have made steps in that direction. In 2018 the Chameleon Academy Podcast (formerly Chameleon Breeder Podcast) reported on an experiment done by Pete Hawkins in the UK on raising a female veiled chameleon using UVI 3 and with no dietary D3. We do need a way to measure success and the best method available to us is at the chameleon’s greatest need for calcium. That would be the production of a clutch of eggs. If the female is low on calcium, the eggs will often show translucent spots. So this was a way for us to gauge UVB effectiveness. Using UVI 3, Pete was able to get multiple clutches of eggs that were fully calcified. That happen to correspond with the beginning of the basking values for Ferguson Zone 3. But this needed to be reproduced and questions asked. Would a higher UVB produce better growth? Can a lower UVI produce a calcified clutch of eggs? Is 30 minutes under UVI 6 the same as 60 minutes under UVI 3? (And the list goes on!)

And so, I took up the baton and I reproduced his experiment and I, too, was able to get a clutch of fully calcified eggs from a female exposed to UVI 3. But I went a step further and replicated the experiment and ran a pair at UVI 6 in parallel. The UVI 6 pair did not show increased growth or any other observable indication that a higher UVI would benefit.

Jonathan Hill of iPardalis tried UVI 3 with Panther Chameleons and, as of 2021, is now on his fifth generation of healthy babies under those conditions. So there is more evidence that this is something we can count on. Of course, this only means that UVI 3 at the basking area is an effective value. It does not mean it is the best value! There may be other aspects that we will discover that will guide us to a higher or lower value for each species. There is still so much work we have to do to refine our husbandry values.

For further research on today’s topic, read the paper that presented the Ferguson Zones. As you read this, keep in mind the enormous amount of work that went into gathering, compiling, and interpreting the data. That is the kind of scientific discipline we need to have. But also do not consider that because it is in a study that it is final. Let this empower us to build on this work by taking the next steps to verify and refine our body of knowledge.



Also listen to the podcast episode where Pete Hawkins describes his experiment testing UVI 3 as an effective UVI for chameleons. I also talk about my repeating of his experiment and adding an additional part of my own. As you listen to this I’d like you to realize how simple it is to create data points. The advantage we have as hobbyists is that we do not have to write a peer reviewed paper. We do an experiment and then see if others can reproduce the results. That is our peer review process! But it does take some discipline to reduce the variables in our experiments to make the effort meaningful. This is hard to keep up for 6 to 12 months or more. Listen in and see if there is a way you would like to be part of this cause.

Implementing UVB: Know our goals. Know the tools

Our goal for including a UVB light is to provide our chameleon the option of basking in enough UVB that their body can produce the necessary Vitamin D3. On the other hand, we are aware that too much UVB can cause health problems (sunburns, eye issues, and decreased fecundity). Thus we want to make sure that the range of UVB in our cage is both effective and safe. Our execution of this requires us to decide on the Minimum Effective UVI as well as the Maximum Safe UVI.

Minimum Effective UVI: The minimum UVI that must be present in the cage for the chameleon to make the required amount of vitamin D3.

Maximum Cage UVI: The highest UVI that we want the chameleon to have access to in order to avoid UVB “overdose”.

These numbers are exceedingly difficult to nail down with certainty as needs will change by species and lifestage. But all we need is a magnitude. We are including in the cage ample space to hide and get UVI 0 so our main focus is on determining the Minimum Effective UVI. But we are cognizant of the Maximum Cage UVI because, as we will find out when we take UVI readings, the levels coming off of our lamps in the first inches are beyond what is seen on Earth naturally. This is no place for an exposed belly of a chameleon walking upside down on the cage top!

My personal goal is for us as a community is that we are so proficient with our UVB implementation that we do not need dietary vitamin D3. You will note, though, that the advised supplementation routine here does include one or two doses of a supplementation that includes vitamin D3. The benefit of this is that it is generally accepted that vitamin D3 and vitamin A have a relationship with each other and it appears to be a good policy to give them together. Thus the supplementation of preformed vitamin A will be done with vitamin D3 for now. So, this is not to try to make up for a failing UVB lamp. It is unknown how much help a twice monthly dose of D3 would give in a cage where the UVB has failed.

The Minimum Effective UVI

There is much on going work to determine what the minimum effective UVI is for different species of chameleons. The greatest amount of work, so far, has been done by Dr. Gary Ferguson with panther chameleons. The Ferguson zones were named after him and they list the Veiled, Panther, and Jackson’s Chameleons in Ferguson Zone 3 which is UVI 1-2.6 with a maximum of UVI 7.4. (If you are interested in the discussion about Ferguson Zones, a thorough paper by Dr. Francis Baines discusses UVB in the captive environment. https://www.jzar.org/jzar/article/view/150/89)

The Jackson’s Chameleon was listed as Zones 2-3, though feedback from the hobbyist community suggests that the Jackson’s Chameleon belongs in zone 3. Testing will continue, but I would lean towards zone 3 rather than 2. Once again, all these numbers are there for us to use as a step for further testing. They are not meant to be definitive. It is our responsibility to take the hard work done by these scientists and expand and add to the collective knowledge. Remember, they have all reptiles, amphibians, and other animals they work with. We live and breath chameleons. It is OUR responsibility to continue their work and add to what we know about chameleons. Expanding on their work is NOT saying they are wrong. It is being actively involved in the work instead of passively consuming. The more people experimenting the better.

The Ferguson Zones were derived from interpreting the natural data and provide a reasonable starting point for us to take it to the next level. We in the chameleon community need our UVB to provide enough energy that a female can lay a fully calcified clutch of eggs. This is the final confirmation check we use to refine these numbers. It is absolutely true that babies, adults, and gravid females may need different amounts of UVB, but with a proper cage set-up the chameleon will have the option to UVB bask and hide as much as they need.

The calcified egg test was performed for Veiled Chameleons by Pete Hawkins and myself where we confirmed that UVI 3 was sufficient to provide for a calcified clutch. This does not mean that UVI 3 is the Minimum Effective UVI, but it is an effective UVI and we will use UVI 3 as the target UVI in our set ups because of this confirmation.

Jonathan Hill, of iPardalis, shared with me that he has raised up three generations of panther chameleons under UVI 3. He used a variety of bulb/fixture/distance configurations, but tuned them in with a Solarmeter 6.5 to UVI 3 at the basking branches. The results are stunning. This is significant because his only supplementation was using the Arcadia EarthPro-A which has no vitamin D3 (or preformed vitamin A, for that matter). This is an implementation of the multi-generational test well over with four generations of eggs produced where the mothers and their mothers have never had synthetic vitamin D3. Their vitamin D3 came solely from UVB at UVI 3. So this establishes UVI 3 as a valid effective level for panther chameleons. Of course, this does not mean UVI 3 is the Minimum Effective UVI. But we know that UVI 3 is in the Effective Range for both Veileds and Panthers by the passing of the calcified egg test.

I am confident that we have further refinement of this number in the near future as more and more members of the chameleon community test these UVB levels and supplement with vitamin D3 free powders.

3rd gen Panther Chameleon from Jonathan Hill

This is a third generation male Panther Chameleon that has been raised under UVI 3 and supplemented with only Arcadia EarthPro-A. The significance of this is that there has been no synthetic Vitamin D3 or Vitamin A in this multi-generational colony maintained by Jonathan Hill, of iPardalis.

4th gen Panther Chameleon eggs from Jonathan Hill

Fourth generation well calcified panther chameleon eggs produced by three generations of panthers raised under UVI 3 and no supplemental vitamin D3. This is from a multi-generational colony maintained by Jonathan Hill, of iPardalis.

The Maximum Cage UVI

In nature, chameleons get one UVB level at a time. They do not get twice the UVB just by crawling up a couple of inches. Our lights, on the other hand have a distinct gradient and we must be smart about it if we are to provide the right levels over the right area without allowing our chameleon to wander into dangerous UVB levels. Since UVB damage is not only in intensity, but also in duration of exposure this is a difficult parameter to determine. Presently, the one controlled study I am aware of is a personal study I performed to compare the effects of Veiled Chameleons raised under UVI 3 and UVI 6. I saw no increased growth with UVI 6 so I determined there was no benefit to giving more than 3. Although this was not meant to determine if 6 was a health level for long term usage I can at least put a stake down and suggest that there appeared to be no issues at UVI 6.  Though, as the commonly respected Ferguson Zones lists UVI 7.4 as the maximum for zone 3 you’ll find I have shifted my Maximum Cage Level on my graphics from 6 to 7.4. This is to make it simpler for people learning to make connections. Panther Chameleons are at a lower elevation so the argument could be made for erring on the lower side for them. Yellow Crested and Machakos Hills Jackson’s Chameleons show similar basking behavior (out in morning and retreat in afternoon) and come from about the same elevation as Veileds so the numbers would, presumably, be able to be used for a start point. The higher in elevation a chameleon lives the more UVB it is exposed to simply because the higher the altitude the less atmosphere filtering happens.

Learning to Effectively Use the UVB Gradient

UVB gradient map for chameleons

Gradients are inherent in the UVB lamps we use and we must use them wisely.

Every UVB lamp has a rough cone-like shape of UVB emitting from it. (A linear bulb would have the cone shape if you viewed it from the ends.) This cone can be broken up into the following sections for ease of understanding and execution:

Caution Zone: Readings directly off the UVB bulb will be unearthly. For perspective, UVI 13-15 is around the maximum we are recording in the standard chameleon habitat at high noon. The highest UV Index measured on Earth is UVI 43 on Bolivia’s Licancabur volcano. Within an inch or two of these artificial UVB lamps you can easily see UVI 40 or even up past 150 where one has to wonder how accurate the meter is! And these are measured through the filter of one layer of screen. To be sure, the UVI level drops dramatically each inch you move away, but, especially with babies that crawl the top panel, we need to be very aware of the levels directly off our lamps. If we do not elevate the lamps then we allow our chameleons to expose themselves to ultra-high levels of radiation. We do not know exactly where the dangerous UVI starts, but I believe I am reasonable in assigning anything beyond what a chameleon could possibly encounter on Earth into the caution zone. We do not know where the dangerous intensities start and there, assuredly, is not a simple value.  As I have personally tested UVI 6 to be effective to raise a Veiled Chameleon, but not show an advantage over UVI 3 we can use UVI 6 as the upper limit of what we target for the inside of the cage. The Ferguson zone method places this value at UVI 7.4 so there is general consistency in experiments and extrapolation. Therefore I will use 7.4 on the graphics to avoid confusion.  This becomes a major husbandry consideration as placing T5 bulbs, the most popular form, directly on the screen top will introduce levels way beyond this into your cage. Remember that these lamps were designed to produce enough UVB that it can reach a basking lizard on the floor of the cage. When we set up a system for arboreals where the lizard can crawl up to an inch or two of the bulb we must adjust our implementation. This is a prime example of how important it is to understand the tools we work with. Thus, any value over UVI is consider in the Caution Zone and is best kept above the cage.

Basking Zone: This is the most important zone to turn our attention to and to experiment with. This will include the values of UVB we want inside the cage. With the information we presently have, the basking branch should be placed so that the back of the chameleon would be in UVI 3. So, made simple, the basking branch is around UVI 3 (or just below a couple inches to account for the height of the chameleon) and the top of the cage is at UVI 7.4. Below the basking branch the UV Index will dissipate to minor levels. We have not shown where the minimum effective UVI is for chameleons so, until more tests are run, we will accept the lower limit of UVI 1 suggested by Ferguson zone 3. But where UVI 1 occurs is not a design issue. What is important is to place the UVB bulb so that your maximum UVI is at the inside top of the cage (we are selecting UVI = 7.4 until better testing gives us another number) and then the basking branch is placed so that the back of the chameleon is at UVI 3. The zone between the top of the cage and just above the basking branch is the basking zone.

Selecting a UVB Profile

To select the proper UVB solution consider the shape you would like the UVB to take in your cage. By learning the principles here you are able to make an intelligent decision as to which UVB lamp to use. But, by far, the most useful and used form of UVB is the T5 High Output fluorescent bulb. They are available from 2% UVB strength to 14% UVB strength (the percentage of light output in the desired UVB wavelengths). And we further modify the strength by the fixture and the distance above the cage. You can select a UVB lamp with the following steps. Note that if you are confused with all these options and just want to put together your cage there are build guides provided that require no deep understanding of the secrets of the universe! So if you don’t absorb everything here do not worry. You can always build an effective cage set-up with the build guides and come back to soak in the fine details.

  • Find the lamps that cover the cage area you wish to have UVB. With the vertically orientated “pillar” shape cages this is generally the width of the cage. So a 24” wide cage would use a 24” wide fixture. You do have an option with the wide format cages to irradiate just the open area. If you recall, the Forest Edge concept applied to a wide format cage has one half of the cage open and one half is dense leaf cover. UVB is needed only in the open area to simulate the chameleon being able to hide in the dense foliage. So, with a 45” wide Dragon Strand Large Atrium a valid design option would be to use only a 36” UVB fixture or even a 24” fixture. Chameleons have been shown to recognize and specifically bask in UVB even when it is separated from heat so you do have the option to make a UVB area in your cage.
  • Review the different configurations of the lamp size that will give you the UVB gradient that provides a UVB Working Zone which covers both the height and length of your chameleon.

Giving UVB recommendations is a tricky thing. The same bulb can give very different results depending on the fixture it is in, the nature of the reflector, and the age of the bulb. Therefore, the graph shown here will be for specific lamps. The Arcadia ProT5 line is, by far, the preferred product simply because it is a bulb and fixture packaged together so any numbers I share here are able to be reproduced in your set-up. Any attempt to give UVB advice that does not include fixture and whether it is going through screen will be haphazard at best. Even my previous versions of this page which specified a single bulb fixture or a multi-bulb fixture would have various results depending on which fixtures were chosen.

Test conditions:

The UVI chart that follows has been tested with lamps that were run for at least 100 hours and had been on the day of the testing for at least 30 minutes. All numbers given here, unless specified, were tested through the screen of either a Dragon Strand cage or a ZooMed Reptibreeze cage. Both Dragon Strand and Reptibreeze screen had the same filter effect.

Having your own Solarmeter 6.5 is the best approach!

The absolute best way to set up a UVB system over your chameleon cage is to have a Solarmeter 6.5 UVI meter. That way you can measure your exact lamp strength and create a custom configuration. You will also be able to track the lamp’s slow degradation over the year and adjust when necessary. The problem with making a chart such as the one below is that readings can change dramatically depending on where the meter is sitting or how it is pointing. Each lamp will give a different reading depending on how long it has been on and how long it has been in use. Thus you should expect that these are magnitude numbers only. They are enough to get you started.

IMPORTANT: UVI measurement is highly imprecise. The level read depends on lamp active age, lamp on-time, brand and shape of reflector, position of the meter, and angle of the meter. The most accurate way to tune in your UVB lamp is with your own Solarmeter 6.5 meter. These charts provided can offer a snapshot of a sample of these bulbs.

UVB penetration map

Chart 1: Depth of UVB light from various commercially available UVB bulb and fixtures

The Compact Fluorescent Light (CFL)

Compact Fluorescent Lights (CFLs) were developed to bring fluorescent technology to the wide spread screw-in light sockets. CFLs have gotten a bad rap in the chameleon world because of the under powered bulbs included in the ubiquitous Chameleon Kit. But they are a tool like every other lamp and need to be used properly. Even the low powered 13W bulbs have use in baby cages. But we should not do a broad brush across all CFLs because of the 13W 5.0 in the Chameleon Kit. When you jump up to 26W lamps you are getting respectable penetration. In fact, as the chart below shows, most CFLs will require you to prop them up above the cage to ensure you don’t get unnaturally high levels of UVB in the cage. For example, I placed an Exo-Terra 26W 200 on top the cage any chameleon crawling on the screen under it would be blasted by a UVI in excess of 150. I caution the community to be careful of making over reaching statements regarding CFLs. The Reptisun 13W 5.0 CFL is the baby brother of some pretty intense lamps.

The measurements below were taken with a 10.5″ reflector so the resulting UVB area was quite satisfactory for a standard chameleon. Smaller reflectors will focus the UVB beam a bit more.

CFL UVB map for Chameleon cage

In Conclusion

Give it some time to sink in. It took me years to figure all this out. I tested every bulb that was available (at the time) and then learned I had to test multiple bulbs of the same kind and then learned I had to test them over time because of output changing with age. So, no, this isn’t easy. I have revised my teaching approach every year to take into account feedback from the community. The way to get better is to simply keep learning and trying out what you have learned in as many different situations as possible. 

And we keep going, keep learning, and keep sharing

And I would like to make this point to highlight that not only are we able to do testing on our own as a community, it is actually more effective when we do that testing. We are the ones who work with chameleons day in and day out for years. Who else is as qualified to establish parameters for chameleon husbandry. And there is another side to that. Who else are we waiting for to discover the parameters we need to be more effective in our chameleon herpetoculture? Scientific studies are wonderful. But, in the end, we are responsible for the growth of chameleon herpetoculture.

And that is the core of what drives the Chameleon Academy outreach.


This module is part of a class on Setting Up Your Chameleon’s Cage where you learn how to build up a complete chameleon environment from start to finish. From this point you can either go back to the home room and see the other modules in this class or go on to the next module where we dive into how to use plants in the chameleon cage!

"Setting Up Your Chameleon's Cage" Home Room

panther chameleon in big cage

Next Module: Setting Up Chameleon Hydration

female parsons chameleon in the rain