Advances in Reptile Lighting

A resource for all reptile keepers

what's all this about?
find out about UV light
the vitamin D story..
the meters we are using in our tests
all about sunlight
the UV requirements of different species
UV transmission tests
UV lighting for reptiles
Introduction to the 2005 Lighting Survey
fluorescent tubes on test
compact fluorescents on test
mercury vapours on test
merc vapours for large enclosures
more info soon..
further reading
related websites
meet the team


UV Guide.co.uk - Ultraviolet Light for Reptiles

The 2005 Reptile Lighting Survey is now extremely outdated. Many of the lamps are no longer on sale; others have different specifications; and new products have been launched.


An Introduction

(This introduction is still valid)

As we have seen, when choosing a lamp for a vivarium, the question we must ask is  "How much UVB does my reptile need, given its natural environment and basking preferences?"

Reptile products vary enormously in the amount of UVB light they produce, and in the type of beam created. These very different lamps would be suitable for very different species of reptile. The chart below summarises the features of the lamps on test.


The main types of lamp used to supply UVB in the vivarium.

Type of lamp

Beam characteristics
(more details)


Fluorescent tubes

Tubes supply a diffuse “glow” with low intensity visible light, little heat, and a fairly uniform UVB gradient, over a relatively large area, resembling natural UVB “in the shade” on a sunny day.
Compact Fluorescent Lamps

Compacts provide a more intense UVB gradient concentrated in a smaller area, but still provide only fairly low intensity visible light and little heat.
Mercury Vapour Flood Lamps

True “flood” lamps produce a more intense UVB gradient concentrated in a smaller area. These lamps also produce heat and more intense visible light, but it is still supplied as a diffuse “glow” rather than a beam.
Mercury Vapour Spot and Narrow Flood Lamps (externally ballasted and self-ballasted)

Because these have a focused beam, they produce very bright light and high UVB concentrated like a patch of sunlight. Self ballasted lamps produce more heat and an even more intense visible light.


Between August 2004 and July 2005, we tested a total of 88 lamps of all types and brands available to reptile keepers in the UK; we launched this website in July 2005. Since then, we have continued long-term monitoring of a range of the original lamps and we continue to test new products. Reports of these tests will be published on this website as they are written.

In our study we have looked at the entire UVB output (between 280 and 320nm of the electromagnetic spectrum) of all types of lamp. We have investigated in detail the initial output of a new lamp; the decay in the output of a lamp with time; and the characteristics of the UVB “beam” for each type of lamp – how far the UVB light extends from the lamp and in what directions.

We have also looked at the effects of reflectors, and of screens and mesh, on the output of these lamps.

We are not scientists, and our tests were not carried out in laboratories. All of our readings were either made on lamps actually in use in “real” vivaria – our own, those of our friends, and fellow hobbyists – or on lamps placed in simple test rigs in our own homes. Variations in the room temperature, fluctuations in the household electricity supply, even the amount of dust on an older lamp in someone’s vivarium will affect the results to some extent.

Vivaria come in all shapes and sizes with walls reflecting different amounts of light. It is simply very difficult to line up a meter perfectly with a steel tape measure, the tip of which is just touching a lamp three feet above you, and take a reading whilst a curious green iguana is trying to jump onto your shoulder. Nevertheless, we have been surprised by the consistency and repeatability of the readings obtained with the Solarmeter 6.2.

What we cannot measure…
Our results cannot be used to compare brands, and determine which lamps are the best at stimulating vitamin D3 production. For that, the exact proportion of ultraviolet light in the wavelengths 290 - 315nm produced by each lamp must be known. To obtain that information, detailed spectroradiograms of lamps of each brand must be obtained using powerful laboratory instruments, and compared with the ability of the lamps to produce vitamin D3 using in vitro biochemical tests in the laboratory.

Researchers including Jukka Lindgren in Finland and William Gehrmann in the USA are conducting pioneering work on this right now. We await their results eagerly, and will report on their findings as soon as they are available. Last year, Lindgren published the first work in this field, which can be read online at: http://www.testudo.cc.

Lindgren developed the concept of a “D3 Yield Index” – a comparison between the vitamin D-producing ability of a lamp with that of the sun. Among the lamps he tested, were several fluorescent lamps currently on sale in the UK: the Exo Terra Repti Glo 2.0, 5.0 and 8.0, and the Zoo Med Reptisun 5.0. He found the Reptisun 5.0 to have the highest D3 Yield Index of all the strip lamps he tested, owing to a high output in the 290 - 315nm range. However, the Repti Glo 8.0 and 5.0 also performed well compared with other lamps in the test.

There is yet another reason why it is not possible for us to compare different brands of lamp directly with one another. Different makes of lamp have different spectral power distributions - that is, they emit different amounts of UVB at each wavelength.  Hand held “broad spectrum” UVB meters such as ours have a fixed peak sensitivity; ours is between 290 -300nm. If two lamps, in theory, put out equal amounts of UVB, but one lamp emitted most of this at 295nm, the other at, say, 315nm, the readings on a Solarmeter 6.2 would be somewhat higher for the first tube than for the second.

…And what we can!
While it is important to know which lamps enable production of the most vitamin D3, it is also important to know how different lamps actually supply UVB to our rept
iles in the vivarium, and it is this which we have been able to study.

Different lamps vary enormously in the amount of UV light they emit, and in the type of beam they produce. If two lamps produce, for example, 20uW/cm² of UVB at 12” distance, but one lamp has a beam that is twice as wide as another, then a large reptile sitting 12” away, which cannot sit completely inside the beam, will be able to produce more D3 from the lamp with the wider beam.

It’s also very useful to know how much the output of a lamp decays with time. Good UVB lamps are expensive, because of the quality glass, phosphors, arc tubes and so forth that go into their production, and because many mercury vapour lamps are actually hand made. One of the first questions we all ask, when buying something expensive, is “How long will it last?” We also wonder, quite naturally, whether it is necessary to follow the manufacturer’s recommendations regarding replacement of tubes every six, eight, or twelve months?

Our study examines the characteristics of each type of lamp in turn, so that the advantages and disadvantages of each type may be considered by anyone wondering what to choose for a particular set-up or species of reptile.

Collecting the Data.
Details of the simple measurement techniques we used.


Coming soon: We now have a spectroradiometer and will soon be publishing our spectrograms of the lamps on test. We are also using a new broadband UVB meter, the Solarmeter 6.5 UV Index Meter, which electronically 'focuses down' upon the range of wavelengths responsible for vitamin D synthesis.


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