UVB
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What is it?
UVB stands for "Ultraviolet light, type B" and is medium wavelength (280–320 nanometers) ultraviolet light. Although UVB itself are measured by its nanometer output, its useful output is measured in µW (microwatts). It is normally emitted by the sun, can cause sunburn and has been linked with cancer.
Why do reptiles need it?
Due to lack of natural UVB in a typical enclosure - the UVB content in direct sunlight is filtered out by normal window glass - captive uromastyx are unable to synthesize sufficient amounts of vitamin D3. Owners need to provide an artificial substitute for this natural source, in the form of UVB bulbs (keepers can of course sprinkle the uromastyx' food with vitamin supplements, but these are shown to be less effective than full-spectrum lighting). These come in several varieties and are dealt with below. UVB must be provided across several photogradient zones, as well as all year round (regardless of photoperiod).
Types of UVB-emitting bulbs
UVB strip lights
Pros:
- Work well
- Easy to use and incorporate into your enclosure
- Easy to find and purchase
Cons:
- Not cheap compared to normal lightbulbs
- Need to be replaced every six months to continue to provide adequate UVB, thereby adding even more to their cost
- Do not produce any measurable heat, thus necessitating the use of auxiliary heat
- Generally n eed to be within 30cm/12" of the lizard for it to gain full benefit
Compact fluorescent (CF) lamps
There have been many studies indicating that compact fluorescent lamps can be dangerous to your lizard's eyesight, and as such should not be used. You can read the research here and here.[clarification needed]
Mercury vapor bulbs (MVB)
Mercury Vapor Bulbs provide (in most instances) heat as well as UVB. These bulbs last longer then typical tube style UVB bulbs do. In general, a good MVB (such as the Mega Ray should last approximately one year or longer with sufficient UVB output. For the most part, replacement every year is recommended unless you have a UVB meter. Some bulbs have been known to output sufficient UVB much longer, but must not be lowered closer to the basking platform so close that the Uro could be burned.
Self Ballasted MVB bulbs are the most common, and produce heat as well as UVB.
External Ballasted MVB bulbs are also common, although not as widely used by the 'average' keeper. These bulbs emit UVB only. They emit very little heat and need to be used in combination with basking bulbs.
Alternative sources of UVB
The best source of UVB is, of course, unfiltered sunlight. However, if you are going to have your uromastyx receive direct sunlight (in an open enclosure outside, for example), you must make sure of the following:
- it is in an enclosed area that it can't escape from
- it has enough room to run and move around
- it is protected from predators
- it still has a selection of cool, shaded places to hide
- the unfiltered element is important - this means direct sunlight! Any type of glass will filter the useful UVB out of the sunlight.
Even taking all of this into account, it is recognised that natural sunlight is not available all year round, or in all weather conditions. A UVB-producing bulb should therefore always be available inside the permanent enclosure.
Controversy with other bulbs
A UVB meters owners' group[clarification needed] tested a new Zoo Med 100W PowerSun and it had a UV index of 20 at a distance of about 30cm (12"), which is about twice the recommended rate at any basking spot. Apparently, the phosphor coating had been thinned (presumably in a cost-cutting measure) making it very uneven, with some bulbs even having holes in this phosphor layer; this allowed high radiation spikes through the coating. It is not currently known if the 160W model suffers from this same manufacturing flaw, but for health reasons it is currently recommended to avoid this brand of bulb. It is, of course, always best to check the UV output yourself if possible, with a UV/solar meter.
