Shining a Light on your Reptiles – Utilisation of UVB Lighting

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Utilisation of UVB Lighting

Shining a Light on your Reptiles – Utilisation of UVB Lighting

Shining a Light on your Reptiles – Utilisation of UVB Lighting

The Reptile Keeping community has seen huge changes over the last 10 years. From the boom in naturalistic keeping, to a greater understanding and application of heating and lighting in the vivarium. We have managed to improve captive Reptile welfare 100-fold.

Usually, we would see advancements and improvements come down from the top end keepers, the experienced leaders in our communities. These would normally filter down slowly to less experienced or new keepers over several years.

However, this latest round of improvements has swept across the community at lightning speed, hopefully for the better. But this does come with a downside. Both topics are a lot more complicated and long-winded to get your head around, especially when you have a hundred comments to read through, all explaining it differently and confusing matters.

In this article, we shall try to break down the difficult topic of heating and lighting to its basic level and explain how to set up the enclosure to ensure your Reptile gets exactly what it needs, in a safe and measured way.

What is UVB Lighting for?

Let us, for a moment, imagine you are new to keeping Reptiles (you might well be, as you read this, in which case Kudos for jumping into research straight away). You know you want this Reptile; you’ve researched where it is from and how it lives, but there is still one contentious point. Lighting!

On the forums and Facebook groups, you asked a question about what lighting you needed, and a fight started. People screaming that X species doesn’t need lighting, they’ve never used it in 30 years and their animals are ‘fine’. Then there are the others shouting that all Reptiles should be provided UVB lighting. Rather than help you, the OP, they are flaming each other and have forgotten entirely about your question. Perhaps that is why you are on this website now?

Straight off the bat, we will tell you now, we are members of the second camp. But why?

In a nutshell, UVB light is generated by the sun, so hits all species that don’t spend their entire lives deep in caves. Even nocturnal species will be exposed to some level of UVB light whilst they sleep in tree canopies, or during dawn/dusk.

UVB light helps to generate Vitamin D3 in the skin, which in turn helps distribute and store calcium in bones, alongside having benefits for the nervous system, muscles, digestion and many other functions. Without UVB light, bones become soft and rubbery, which is called Metabolic Bone Disease (MBD) or Rickets.

Study after study have shown that most life on earth have evolved to utilise this free source of energy for the same reason, so it must have a deep history within the evolutionary process stretching over 500 million years (Holick, 2003). Therefore, it is a fair assumption to suggest that all species we keep in captivity will benefit from the addition of measured and controlled UVB light in an enclosure. How we provide that for different species, will vary though.

How does it work?

The process for converting sunlight and various other compounds in the body is relatively complicated and beyond the scope of this article. For the new keepers and novices that this article is aimed at, it’s a case of ‘just accept it works’. And to be honest, its beyond our ability to properly explain it, but we shall include some links to resources at the bottom, so that you can do further research if you wish.

UVB Lighting itself isn’t as complicated though. Consider a torch switched on in a dark room. You should notice 2 things:

  1. The beam spreads out from the source
  2. The further away from the source it gets, the dimmer the light is.

This is referred to as the Inverse Square law, and is shown graphically here:


Inverse Square Law

Fig 1 (Sarah Simmons, 2017)

Every Light source has a set energy release per second. As you move further away from the light source, that energy is spread over a wider area, and so becomes less intense. Now imagine that the energy is our UVB Lighting. Close up to a UVB source, the UVB energy is concentrated and therefore, high. But as we move away from the source, it becomes less intense.

To measure UVB Lighting in terms of use for animals, we use the Ultraviolet Index, or UVI. You will probably be aware of this system from checking the weather. They will either say the UV Index is low, or give it a figure, usually as a round number, but it can be decimalised too.

Close up to a UVB Lamp, you may get a UVI of 50 or more, which is ridiculously strong and wouldn’t be encountered anywhere on Earth, however as you move away from the lamp you will see an exponential degradation of the UVI Lighting. It’s this change due to distance, that allows us to setup our enclosures with a UV gradient, allowing our Reptiles to choose how and where they bask. This can be shown by placing a UV Iso-Irradiance chart over an image of an enclosure (Image is illustrative only)

Setting up the Lighting

Now we know the basics of how UVB Lighting works in an enclosure, we can use this knowledge to setup an enclosure perfectly for our Reptiles. But there is still some information we require:

  • What range of UVI does our Reptile need?
  • What is the UVI output of the lamp we are using?
  • What is our Reptiles Environment type?
  • How does our Reptile behave?

What Range of UVI does our Reptile need?

The very first question we are asking is, what level UVI do we need? The answer to this question will not only help with positioning décor correctly but will also help you with choosing the right brand and strength UVB Lighting tube.

For the purposes of this article, we are going to go with that most Staple species of choice, the Bearded Dragon.

In the past, we would now have to scour information from all over to see what the best UVI range is to use, but thankfully some extremely clever and dedicated scientists and veterinarians have done the hard work for us, and created the UV Tool:

How much UVB does my reptile need? The UV-Tool, a guide to the selection of UV lighting for reptiles and amphibians in captivity.

In this paper, there are hundreds of species of Reptiles and Amphibians, with details including UVI range, Basking temps, Ambient temps and behaviour/environment types. It is easy to use, whether you are a novice or long-term keeper and will improve the welfare of captive animals for decades to come.

There are several steps to get the right information, which I will detail below, but if you go through it methodically, it shouldn’t be an issue to anyone. Even young kids can get involved in matching the information, which is a great way of letting them feel like a part of the project and will no doubt enamour them into Reptile care for the future.

Have a full read through of the entire paper. Some of it may go over your head (it still does for us) but having a more rounded understanding is never a bad idea. However, if you are not that way inclined, then open up the ‘Tables and Figures’ for the easiest way of navigating through the documents.

Open UV Tools – Ferguson Zones, Figure 4 of the documents, which shows the Ferguson Zone chart. This was devised by Prof. Gary Ferguson, as a way of categorising Reptiles into zones, for ease of studying their UVB requirements. We will come back to this later.

Next up, find the Table that will refer to your chosen species. In our case, this is Table 4 – Lizards. Within the table, search for your animal. If you don’t know the scientific name, there is a list of common names but be aware, common names aren’t the best identification tool as multiple species may have the same name. Try to use the Scientific, or ‘Latin’, name. It is also worth taking note of the column titles, as they do not run through the tables.

Here’s the entry for a Bearded Dragon, Pogona vittceps:


Here we can see that we have the following information:

Latin Name: Pogona vitticeps
Common Name: Inland Bearded Dragon
Biome: 07/08/12/13
Ferguson Zone: 3 to 4
Photoperiod: 13:11/14:10
Winter Treatment: Cooling/Brumation
Basking Zone: 40-45°C
Day Ambient Air Temps: Summer – 25-30°C Winter – 25-30°C or 15-20°C if Brumating
Night Ambient Air Temps: Summer – 20-25°C Winter – 20-25°C or 10-15°C if Brumating
Microhabitat: EFG

To decipher the information, we now need the Key from Tables 2&3, shown below:

The Latin and common name are easy enough to understand, but what is a Biome? The Biome is simply a generalisation of the type of environment a species comes from, this goes hand in hand with the Microhabitat to determine what sort of natural environment you are trying to mimic, and how the animal uses that environment, especially in terms of heat and light.

Bearded Dragons come from Biomes 07/08/12/13 which translate as:

07 – Tropical and Subtropical Grasslands
08 – Temperate Grassland, Savannah and Shrubland
12 – Mediterranean Forests, Woodlands and Scrubs
13 – Deserts and Xeric Shrublands

So instantly, we can see that they come from quite a wide range of environments types, but how they use those environments is key to our setup, and that is the Microhabitat. Bearded Dragon Microhabitats have been classified as EFG:

E – Foliage or Shrubs
F – Grassland and Savannah
G – Semi-arboreal

This gives us a good understanding of their environment type. They will generally hang around trees and shrubs, where they have access to shade and humid areas, as well as protected burrows from the elements and predators, whilst accessing the open savannah and grasslands to bask.

With that worked out, we also have their Ferguson level set as 3 to 4. This is where the Ferguson Zone chart comes into play:

Ferguson Zone 3 to 4 places them squarely into the Open or Partial Sun Basker and Mid-day Open Sun Baskers range. From here, you need to make a choice based on your enclosure. For most keepers, a Bearded Dragon is going to be kept in a 4x2x2ft (Hopefully, we will see this minimum size range increased in the coming years, as improvements and understanding change). For that size enclosure, you want to remain within the Ferguson Zone 3 range, but if you have gone all out and created a huge enclosure (let’s say we are going to do an awesome 6x3x3ft enclosure) then stretching into Ferguson Zone 4 will be possible. This is because, the larger enclosure allows greater options for open basking, into full shade with a better light gradient.

So here we have our 6x3x3ft Bearded Dragon enclosure, we are creating a naturalistic setup with a nice deep substrate and plenty of climbing ability for this Semi arboreal, Shrubland setup. We know we can use Ferguson Zone 3 and 4. The third column along is the most important, as this is the UV range we are looking at for general use, i.e. outside where our surface temperature reaches the 40-45°C mentioned in column 7 of table 4. This gives us a UVI across the two zones of 1.0 to 3.5.

At the point of basking, with a large enclosure, we can stretch into the Max UVI recorded. Though, it would be recommended to keep this to the lower region, in our case 4.5 maybe 5 Max. There may be points where they can access high UVI’s, but these should be avoided at best, and not created as a basking zone at all.

But Wait! How do we know what the UVI is at any point?

There are 2 ways to work out the UVI at certain points. As we learned earlier, UVI is determined by distance from the source of light, it will also be affected by anything that is between the lamp and the area being measured. If you are placing the lamp over a mesh lid, this can reduce the UVI drastically, so will need to be considered.

d457feb4-5a97-4afa-937d-410230c285e2Manufacturers are pretty good at putting figures on their boxes, which for most people, is a good start for setting up their distances and UVIs. However, there are many factors that can affect the output, such as age of lamp, objects in between, and normal tolerances in manufacture. So, if you really want to get the best setup possible, we would highly recommend purchasing a Solarmeter. These are expensive to purchase but will not only help set the enclosure up properly, they will allow you to monitor output over the year. You will soon realise that quality lamps may last a lot longer than the manufacturers recommendations, saving you hundreds over the life of each animal you own.

How you choose to monitor the levels is up to you, and there is no right or wrong answer. The manufacturers readings, at least from highly reputable brands, can be trusted.

Now that we know what UVI we require, and we have checked all the manufacturers recommendations, we have been able to determine which Lamp we should get for our Bearded dragon. The Arcadia Reptile website has a handy little tool that can also assist with picking the right lamp percentage here –

Occasionally, this tool may differ from the UV Tool, so use some better judgement to decide where to go with it. From the information above, we are going to go for 12% T5 UVB Tube. The length of the tube will be based on your enclosure size.

Previously, advice was to use a lamp that is around a half to three quarters of the length of the enclosure, but this has changed over the last year or so and it is now recommended (at least for T5 Lighting systems, T8 Lighting still requires additional length) to have the tube long enough to cover the basking zone, either by going straight along the width of the enclosure to one side, or diagonally to ensure it fits.

UVB Placement by Dr Frances Baines, Reptile Lighting

As our enclosure is 3ft deep, we are going to use the 24w, 2ft tube and place it straight down the width, in line with the heating. With it fitted, we can now switch on the lamp. If you are setting up with the use of a Solarmeter, we would recommend leaving the lamp on for around 12 hours or so to allow the output of the bulb to settle. Initially, they can start off with quite a low output, but this rises over time to a more stable output for measuring.

Now we have all the information and equipment we need to setup the basking area’s UVB. Our lamp is on and stable, so we can take our Solarmeter and start taking readings. Ensuring the sensor is aimed directly at the lamp, press the button and you will get a reading. Move this around in the area where we plan to put our basking light, until we get a UVI of around 4.5 to 5, as mentioned previously. (If you are using manufacturer recommendations, check their recommendations and set up at the distance from the bulb that it states).

Let’s say our prime spot of 4.5 UVI is 40cm from our tube (Slightly off to the left, as our basking spot will be under the heat bulb. We now need to build our basking zone up to that point. As conscientious naturalistic and/or bioactive setup owners, we have a nice deep substrate that has taken up 15cm of the base. We are going to be about 45cm from the roof of the enclosure (40cm for the UVB and 5cm for the size of the T5 unit). This means our basking spot is going to be about 30cm above the substrate. How we get our basking spot to be that high up in this enclosure is a matter of personal preference, and down to our findings regarding the Microhabitat and Biome.

We know that Bearded Dragons are Semi Arboreal and would naturally be found basking on tree branches or fence posts, so for our example, we are going to use a branch to create a flat and perpendicular basking zone at 30cm above the substrate. For other species, or smaller enclosure, you may wish to setup the basking zone over a pile of rocks with nooks and crannies, or even just straight onto the substrate. Once that is in, we can now start placing more branches around, but at varying heights, giving heat and light gradients all over, so the Bearded Dragon has a few choices for basking. It’s also important to use décor, plants and other items to create warm, shaded areas away from the UVB.

And there you have it, your UVB is setup exactly as you need it. Just ensure you either monitor regularly with your Solarmeter or replace in accordance with the manufacturer’s recommendations.

We’re done with Lighing, On to Heating

From here on, the setup gets a little bit easier. We have our basking zone setup for UVB and now need to add heat. We know the temperatures we require, as we pulled them from the data in the UV Tool.

Our Bearded Dragon needs a basking surface temperature of 40-45°C and a warm zone of 25-30°C in Summer. For our naturalistic enclosure, we need to be using overhead heating, and it is always best to use light emitting heat lamps for a few reasons:

  1. A well-lit basking zone presents to the Reptile as a ‘Patch of Sunlight’ and becomes the obvious place for them to bask.
  2. Light Emitting heaters produce a better, more accessible heat than Ceramics. Ceramic heaters work like a radiator, heating the air around it which eventually heats the space. Quality light emitting heaters, especially halogens, don’t really heat the air, they heat objects. The heat penetrates skin deeper, warming the blood vessels of the animal which then gets spread around the animal’s body by the blood.
  3. Light emitting heaters tend to be cooler at the source than ceramics, so if by chance your Reptile jumps and hits it, they will suffer much less damage.

Our aim is to use the right heat lamp, so it is on almost full power, all the time, whilst creating the right temperature at the basking zone. However, we still need to ensure that we use a thermostat, so that if we get hotter than normal weather, the thermostat will dim the bulb down and prevent the animal from overheating.

In our theoretical enclosure, we are going to test 3 different heat lamp wattages, to ensure we meet the requirements for the basking zone. Thankfully, we are aiming for a range of temperatures, so it allows us a little tolerance in our figures.

When we test the bulb, place it into the heat lamp holder and plug that directly into the mains, rather than through the thermostat. This gives us the 100% power reading so we know the maximum temperature our heat lamps will reach in a normal ambient room temperature. (Note: If you are trying to set up the enclosure during a heat wave it may be best to setup at night, when your room is a little cooler).

Test each bulb when the enclosure is as cool as possible, to prevent previous tests affecting your result. So, place the lamp in the enclosure and leave it for half an hour or so to warm up. Take a reading just outside the basking zone with a Digital Thermometer whilst also measuring the surface temperature directly under the basking lamp using an Infra-Red Thermometer. In our example, let’s say we get the following results:

35w Halogen Lamp – Warm End Temperature: 26°C, Surface Temperature: 36°C

50w Halogen Lamp – Warm End Temperature: 30°C, Surface Temperate: 40°C

75w Halogen Lamp – Warm End Temperate: 35°C, Surface Temperature: 45°C

The temperature ranges we are looking for are a Warm End of 25-30°C and a Basking Surface Temperate of 40-45°C. As we can see from our readings, the 35w Halogen has a nice Basking Surface Temperature but is not reaching the minimum requirement for the warm end, whilst the 75w Halogen is the opposite, it reaches the requirements set for the Warm end but the surface temperature exceeds that which we need. However, the 50w Halogen is right within our ‘Goldilocks’ zone, it is just right.

This means we could run a 50w Halogen at full power to reach the correct temperature, with a Dimming thermostat added as a fail-safe should our room ambients drive the overall temperature of the enclosure up. This prevents overheating whilst no one is around to resolve any issues (such as opening a window)

Basking Surface Temperatures will be affected by the medium used in the basking zone. If you struggle to reach the requirements of both readings, swapping the material used in the basking zone. This can drastically change the results and help get our figures in tolerance. For instance, swapping from wood to slate will allow the surface temperatures to rise. This allows you to use a lower wattage lamp when the higher wattage is overheating the rest of the enclosure.

We recommended ensuring that the Basking Zone covers the entire body of the animal. This ensures efficient heating across the body, rather than localised hot spots that could cause burns. If your standard bulb doesn’t cover the body of the animal, it is worth adding a 2nd or 3rd bulb. However, remember to adjust wattages to ensure temperatures remain within limits.

And there we go

You should now be able to setup your basking zones to the appropriate level for your chosen Reptile. Now comes the fun job of planting and decorating your enclosure to provide a natural environment and enrichment for your Reptile to thrive. More on that, in another article.

Author – Tarron Boon
©Bioactive Herps, 2021. All Rights Reserved

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