UV Light and Reptiles

UV Light and Reptiles

As a reptile keeper, or keeper of any pets for that matter, it is up to us to provide everything they need, food, water, a clean habitat, and the correct environment. For reptiles this also includes the correct sort of lighting. We know about a heat lamp to allow them to keep warm enough to function, but what about UV.

What is UV Light?

The sun produces a whole spectrum of lighting, some that we can see, and other that our eyes can’t see, Ultra Violet, or UV lighting is a part of the spectrum that is invisible to us, sitting between X-Rays and visible light. Its UV light that is responsible for sun tan, sun burn and a leading cause in skin cancer. It is also how most land based vertebrates produce Vitamin D3, the micro nutrient essential so we can use calcium to get strong and healthy bones.

When a reptile is allowed access to UVB then cells in their skin begin to produce a chemical, which when the animal is allowed access to warmth via infra-red light (found in all heat lamps) will turn to Vitamin D3. This is the vitamin that is vital for calcium absorption as well as various functions in the body to keep organs healthy.

Why do reptiles need UVB?

If a human was deprived of access to natural sunlight for a significant portion of their life, especially during childhood, they may well develop a condition known as rickets. Here the lack of vitamin D means that the bones have not been able to utilise calcium properly. Similarly if a reptile is denied sunshine then they too will stop producing Vitamin D and so can suffer from a host of ailments, including metabolic bone disease.

Are there other ways to provide these micronutrients?

It is possible to provide Vitamin D3 via dietary supplements, but it is all too easy to overdose via these supplements, there has been no recorded cases of animals overdosing on D3 by basking.

How do I provide UVB?

The best way is to provide natural sunlight, if you live in an area where you can provide an escape proof outdoor enclosure even if it’s only for part of the year then its well worth doing so. Just remember that it can get very hot very quickly so they need to be able to go into the shade if they want to.

Many keeper recommend putting your enclosure near a window for them to get natural light. This is a bad idea for two reasons, firstly they may over heat in the direct sunlight, and secondly most glass will filter out most if not all UVB. Even a small mesh will filter out a lot of the UVB getting to them. Some of the modern glass will allow around 40% of the UVB through, so if you’re looking to replace windows and want your reptiles to be able to get natural UVB, its worth asking about the amount of UVB able to get through.

The most practical and most common method is via UVB lighting. Be careful when choosing a bulb, many provide UVA but no UVB which is the important factor of Vitamin D3 production. Remember when buying your bulb they have a limited life, so check out how long your bulb or tube can last before it need replacing.

There are two main types of bulbs for UVB light, and a couple you may have heard of, but may want to steer clear of.

Mercury Vapour Bulbs (MVB)

A combination of heat, light and UVB the MVB provides everything in one package. However they are the most expensive normally and provide a concentrated UVB spot, meaning there is no gradient across the tank or Viv. Since many reptiles will choose where to lay, and so how much UVB they receive many keepers consider this a problem.

Linear or fluorescent tubes

Probably the most widely used form of UVB for reptiles. They should extend about half to 2/3 of the way along the Viv to allow a gradient, if using with aquatic and semi aquatic species allow to cover both the basking area and some of the water area to allow shy species to ‘bask’ just under the surface. The UVB will penetrate a short distance into the water.

To fit the tube you will need a light system, if using in a wet or humid environment consider using ones designed for fish tanks to reduce the risks.


Whilst there are LED systems that give off UVB at present they are still being developed to be up to the task of providing this wavelength for reptiles. It’s likely that improvements in this area will mean it’s not too long before they are on the market though.

Compact/Coil UVB

Most keepers would advise to avoid these, the amount of UVB produced means that they have to be positioned dangerously close to the animal itself, risking eye damage, or them breaking the bulb itself.

Second hand equipment

If you buy a second hand set up it’s well worth replacing the UVB source with a new bulb or tube, unless you have a UV meter there is no way of telling how much is being put out, and this is a vital part of your reptiles care.

Forest or desert

You might see that there is different percentages of UVB stated on the side of tubes and bulbs, this is to do with the environment you pet comes from. Forest dwelling species, or those most active during the night, or even dusk and dawn, will need lower levels of UVB than those used to running around the desert in the middle of the day. Whilst it may seem easier to put a higher percentage in than they need in fact this could damage their eyes.

Baskers or fully aquatic reptiles

Turtles are one example of a reptile that spends much of its life in the water, but you need only see a line of sliders basking on the edge of a lake, or a musk turtle hanging around in some pond weed close to the surface to see that they do bask, and so do need UVB. Many turtle keepers use the higher percentage tubes for the more aquatic species as the water can create a gradient, but watch out for turtles not basking, or even eye damage after a new tube has been installed. Turtle like many reptiles, can see UVB parts of the spectrum, and so can see when the light is right to bask.

Distance vs out put

The further away from the UVB source the less effect this has on the Vitamin D3 production, so mounting on the top of a tall cage will lessen the usefulness of the tube. Placing too close to the animal may result in eye damage however, it’s well worth researching the natural environment of your pet and seeing how much UVB and heat they would receive in the wild. A UVB meter is a worthwhile investment to monitor the amount of UVB being received and may save you money in the long run, either through not having to replace tubes that are still functioning well, or by avoiding costly vets bills.



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