Ultraviolet (or UV) light is represented in the EMR spectrum (light) as light with a wavelength of 200nm to 400nm. The UV spectrum is broken up into three parts: UV-A, UV-B and UV-C, all of which are present in natural sunlight:

XRay below 200nm

UV-C 200-260nm

UV-B 260-320nm

UV-A 320-400nm

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I

B

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UV light is required by most animals and plants, and each of the three types of UV light are used for different purposes by reptiles and amphibians:

• UV-A is in the visible range, and is responsible for normal behaviors such as feeding, diurnal movement, mating and others.
• UV-B is a non-visible wavelength, and allows the synthesis of vitamin D3, which helps to process calcium and prevent metabolic bone disease. Most snakes DO NOT have high UV-B requirements, as they get the vitamin D3 from the liver of their prey. Amphibians also do not seem to require UV-B lighting. Diamond pythons, lizards and turtles REQUIRE UV-B lighting, otherwise they will develop metabolic bone disease and turtles can also have soft shell problems.
• UV-C is also a non-visible wavelength, and does not seem to be required by reptiles, although little is know about it at this stage. UV-C is often used as the light source for UV sterilisation for killing bacteria, and at high levels of exposure can be harmful to most animals.

UV light is usually added to the enclosure by the addition of a tube that emits either UV-A, UV-B, or both.

Tube manufacturers recommended that you replace the tube at least every 12 months (sometimes sooner), as UV output decreases with time, and after 12 months the tube is no different from a standard fluorescent tube in terms of UV output. A good way to ensure that you change your bulb regularly is to write the date it was first used on the end of the tube in a permanent marker. This way it doesn't matter if you move the tube, change setups or whatever, as you'll always know when it's time to change the tube.

UV wavelengths are filtered by glass and plastic, so it is important that you have the UV bulb within the enclosure, not shining through the top or side. 95% of UV-B light is filtered out by a sheet of glass. Aluminium fly screen filters out 30% of UV-B light, so it's also important to have wide mesh screens over the tubes if you need to protect the animal from burns. In a lizard enclosure, you might get away with not covering the bulb, especially if the lizards you're keeping aren't good climbers. If you're housing a snake, a wide mesh screen such as 'mouse wire' is best, which should allow at least 95% of the light through.

UV light levels also decrease as you move away from the bulb's surface, so it's important that you position the bulb and your cage's furnishings so that your animals can get as close as possible to the bulb - a basking spot 300mm (12") from the bulb is ideal.

Given the variation in prices of the tube, a number of comparisons have been made. Below are links to pages on this site which show the comparable UV output of commonly used tubes.

Test results from SA Fish and Reptile (conducted by Ultra Violet Products)
Test results of UV-A and UV-B output of UV emitting tubes with output measured at various distances from the tube surface, and also on tubes of different ages and dual tube combinations. The following UV tubes were tested:

• Philips TL
• NEC Blacklight T10
• Sylvania Reptistar
• Zoo Med Reptisun 5.0
• Zoo Med Reptisun 2.0
• ESU Desert 7%
• ESU Super Day Light
• Dura-lite Power Twist

Test results from Boston University School of Medicine
Test results of the spectral irradiance of UV emitting tubes over the full spectral range (100 - 800nm) as well as specifically over the UV spectral range (280 - 320nm). The following UV tubes were tested:

• Reptisun 5.0
• ESU Desert 7
• Vitalite
• Hagen Repti-Glo
• GE Coolwhite

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Links to other UV lighting info:

Reptistar (Sylvania) Reptile lighting
Information on the Sylvania Reptistar fluoro tubes. Company hype - "Promotes Vitamin D3 and thus increases your reptile's health, growth and well-being through a high content of UV-B (up to 5%) and UV-A (up to 30%). Improves the natural colours of your reptiles by a 6500 Kelvin full spectrum light with a high colour-rendering index (group 1A)."

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