Tyrannosaurus Pets

A quick guide to UV Lighting

What is UV light?

Ultra violet light is the name given to any light that has a wavelength between that of visible light (to human eyes) and X-Ray radiation.  It is called ultra violet because it is beyond the violet light which we can see.

Ultra violet light is normally broken down into three simple groups UVA, UVB and UVC.  UVA can promote natural behaviour and increase activity, breeding and colour in captive reptiles.  UVB is the one we are most concerned with as this is what stimulates the synthesis of vitamin D3 in reptiles and enables the animals to efficiently utilise the calcium in their diet preventing the onset of metabolic bone disease (MBD).  UVC is highly dangerous and UVC lamps should never be employed in reptile enclosures.  The UVC lamps available in the pet trade are for use in enclosed filtration systems and act to sterilise the water passing through the filter.

Just because we can't see this light doesn't mean that other animals are unable to see in this wavelength.  Many birds and reptiles are able to see UVA light, and the intensity of this light can be used to stimulate breeding and other natural behaviour.  

Francis Baines has produced a short video explaining some of this; it also shows some very interesting graphs of the output of various UV lighting systems.  The link to this is below.

Francis Baines UV Video

UV lighting Systems

The commonly available UV lighting systems are strip or fluorescent lights, compact lamps, mercury vapour lamps and metal halide lamps.

T8 Fluorescent strip lamps

These are the most commonly available and widely used UV Lamps and come in a wide range of sizes and outputs.  These lamps often have a UVB output expressed as a percentage.  This figure is the percent of the lamps total light output that falls within the UVB wavelength.  This is not a particularly good comparison between tubes from different manufacturers because the two different tubes will be giving out different amounts of light.

Most companies making UVB strip lights produce 3 different models

2% UVB lamps

These lamps have a very low UVB output, and a lot of manufacturers are starting to rename them as natural sunlight rather than a UVB tube.  Due to the low level of UV these tubes should not be used as the only UV source in a vivarium.  They are brighter than the other UV lamps and produce a good level of light in the tank.  We use these tubes in all our shop vivariums.  The light from these tubes brings out the colours in captive reptiles, and animals kept in these tanks appear more active than most.

5% / 6% UVB Lamps

These lamps are usually marketed as jungle or forest lamps and are aimed at animals that would normally live under the shade of the forest canopy.  

10% / 12% UVB Lamps

Often called desert rated UV lamps, these are designed for reptiles that bask in the full sun of the desert.  Ideal for bearded dragons these are the most popular style of UV.

The simplest way to think of these lamps is that the desert UV's are twice as effective as the forest lamps, so the UV from a forest tube at 10cm, is roughly the same as that from a desert tube at 20cm.  


Adding a reflector to a UVB Strip light directs more of the light into the tank.  These can greatly increase the amount of UV available to the animal. 

UV Tube Size

Most UV strip lamps are available in a wide range of lengths from around 45cm up to 120cm.  With standard UV tubes it is worth using the longest tube that will fit comfortably in the roof of your vivarium.  The reptiles benefit from a gradient of UV within the tank in the same way as they need a temperature gradient.  As the effective output of the tubes is so much lower than that of the sun the gradient is easily achieved by allowing the lizards to climb and bask near the light source.  They can then return to the floor of the vivarium or into a hide to receive a lower UVB level. 

T5 Fluorescent Strip Lamps

Relatively new additions to the market are Arcadia's D3 and D3+ T5 Strip lights. These are narrower bulbs than the more common T8.  Both the visible and UVA/UVB output of the T5 lamps is far greater than that of the T8 making them a better option especially in taller tanks.  The slightly higher set up cost is offset by the greater output and range of the UVB.  The Arcadia D3+ T5 lamps when fitted with a reflector are able to produce useful levels of UVB at a distance of 60cm from the lamp.  These are available in both 6% jungle and 12% desert strength lamps. 

Compact UV Lamps

These lamps look like a standard energy saving bulb.  Each manufacturer who produces UV strip lights generally also produce UV compacts with the same UV% ratings.  These compacts are not as useful as the strip lights due to the distribution of the UV output.  This is very high close to the bulb but falls off rapidly as you move away.  These lamps are most effective in smaller enclosures.  These bulbs are sometimes used in addition to a strip lamp to offer an increased amount of UVB at a basking spot in the vivarium.

Mercury Vapour Lamps (MVB)

These are high output internally ballasted lamps that do not require a separate ignition system.  They fit into any standard ES fitting but we would recommend a heavy duty system suitable for ceramic lamps as they get very hot.  Due to the design of the bulbs these lamps can not be run through a thermostat, so are only suitable for large vivariums.  They are fitted with an overheat system which will cut out if the lamp gets too hot, because of this they should only be run in open wire clamp fittings not enclosed domes.  Currently available in 100w, 125w and 160w depending on manufacturer the smallest enclosed tank they can be used in is 180 cm x 90 cm x 90 cm.  They are ideal for use in open topped enclosures such as tortoise tables.  Because the output of these lamps is so high they come with a minimum distance from the base of the lamp to the back of the animal.  This is between 30cm and 60cm depending on the brand and wattage of the bulb.  Check the instructions of your lamp carefully.  Like the strip lights not all brands are equal. We would recommend either the ZooMed Powersun, or the Arcadia D3 basking lamp.

Metal Halide Lamps

These are another group of high out put lamps.  Usually these bulbs require a separate ignition system.  Because of this they don't generate the same level of heat as the MVB's making them more suitable for smaller vivariums.  Due to the high output these lamps come with a minimum operating distance of between 20cm and 60 cm depending on brand and lamp wattage. Again check the instructions on your lamp.

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Tyrannosaurus Pets