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Keeping Reptiles Newsletter
 Issue 12  
June, 2005
UV-lamps for Terrariums and their effectiveness - Part 1
In this Issue

Contributed by Michelle T. Nash

Here's a subject that's near and dear to my heart. I've been wondering about this for a long time. Recently, the Chicago Herpetological Society reprinted a translated version of a research article from Finland. I have taken the liberty of copying the Title, Author and Abstract as seen in the CHS Bulletin, followed by my own personal synopsis of the article, with a few quotes from the article sprinkled here and there. I hope everyone finds this helpful.

SOURCE: Bulletin of the Chicago Herpetological Society Volume 40, No.1 January 2005

Original paper "UV-lamps for Terrariums: Their Spectral Characteristics and Efficiency in Promoting Vitamin D3 Synthesis by UVB Irradiation" by: Jukka Lindgren may be downloaded from here

Translated by: Tiina Siitonen, Jukka Lindgren, Barry Brown


Sufficient irradiation within a narrow sub-band of the UVB range is a prerequisite for the photosynthesis of vitamin D3 in skin. Although radiation below wavelength of 300 nm (nanometers) promotes photosynthesis of vitamin D3, radiation above 300 nm destroys vitamin D3 that has been already synthesized in skin tissue or nutritionally obtained. Furthermore, skin temperature has a significant effect on the pace of vitamin D3 syntheses. In a terrarium, the required UVB-radiation has to be artificially produced with dedicated lamps.

In the study, the characteristics of light produced by fourteen different models of UV and full spectrum lamps specifically designed for terrarium use were measured over a range of 250-800 nm. As a reference, the spectrum of natural sunlight was also measured when the sun was at its highest point of elevation in the southern sky of Finland. The proportion of radiation energy that takes part in the photosynthesis of vitamin D3 was determined and the D3 Yield Index was calculated. Significant differences as large as a thousandfold were found in the D3 Yield Indices. The resulting conclusion is that UVB radiation as a percent of the total radiation figure does not necessarily give a true indication of a lamp's capability to maintain cutaneous [(in the skin)] production of vitamin D3.


As stated above, only a certain range of wavelength of UVB rays promotes vitamin D3: (295 -300nm)

The next range up the scale actually is known to destroy Vitamin D3: (315-330nm)

The UVB percentage on packages should not be the sole basis for determining it's ability to promote D3 synthesis in your reptile.

It's the amount of the beneficial wavelength weighed against the amount of D3-destroying wavelength that's a better measurement to consider. And of course the packages don't include this info.

Some UV lights are not meant to promote D3 production, but to merely provide a broad spectrum of light to more closely mimic the wide range of UV found in sunlight outdoors.

Heat helps the skin make Vitamin D3. Eight times more D3 can be synthesized at 25*C (77*F) than at 5*C (41*F)

Here's a quote from the article: "It should be noted that the theory and research discussed above relate to human skin. However, the chemistry of the skin of terrestrial vertebrates is similar enough to that of humans to justify the theory to be extrapolated to reptiles as well." FINALLY, HUMANS WERE USED AS GUINEA PIGS TO BENEFIT REPTILES Hee Hee Hee!

The UV measurements taken on the 14 various lamps was performed at a distance of 30cm (almost 12 inches).

The best lamp tested indicates a D3 photosynthesis rate that is ½ that of the natural sunlight on the summer solstice in Finland - Which we all know is nowhere near the equator - so that means it is not the most preferred UV comparison but as you can figure out, man can not replicate the full magnificence of the sun in these little light fixtures and we are simply trying to provide them with the next best thing. And on a side note, though this was not mentioned or hypothesized within the article, this makes me wonder if we should continue to offer some vitamin D3 supplementation even when providing the best light on the market. Please see the end of this long post to get a basic list of the "best" D3 promoting lights out there.

Note that the measurement of the sun is such that it is only a single measurement of the light encountered during the day and not what would be available throughout the entire day. It would be weaker in the morning and evening where the UVB lamps offer a consistent amount of UVB through the day. My conclusion based on this info is that although the lamps are weak compared to the sun they offer a constant supply of D3 producing light whereas the sun ebbs and flows throughout the day and the seasons so maybe our weak little human-made lights are sufficient.

For those interested in statistics, only one unit of each lamp was used in the testing. Though this is a very small sample of each product, it mimics the consumer's purchase of one lamp per cage so it makes the odds with consumer uses virtually equal.

The D3 yield index is a measurement of how well D3 would be synthesized under the influence of the wavelengths offered by each lamp.

It is interesting to note that they also tested the best lamp after 10 months of use (12 hours a day) to see what kind of reduction in effectiveness there would be. Happily, it is reported that there was a minimal drop in effectiveness. A drop of only about 16 percent was measured. Though I did some calculations based on Table 3 figures and noticed that the ratio of "good" to bad" wavelengths was improved slightly during the 10 months making the drop in "good" wavelengths less serious when it comes to producing & not destroying D3.

"...True-Light [brand] lamps are obviously NOT UV lamps, although their retailer has sometimes recommended them for this purpose." These are one of the lamps that are better for simply illuminating the enclosure.

"The lamp models Repti Glo, Life-Glo, Exo-Terra Repti Glo 2.0, and ESU Reptile Super UV Daylight, emit only a few percent of their radiation in the UVA range, with even less in the UVB range. Active UVHeat lamp also stands out with its rather low percentage of UVB radiation; this is however, a bit misleading, since the nominal power of this lamp is significantly higher than that of any other. Although its irradiance in UVB region is quite high, this is still not a proof of its high capability to promoting photosynthesis of vitamin D3 as shown later."

Next Issue: UV-lamps for Terrariums and their effectiveness - Part 2 (including comparison charts of UV lamps)

Michelle is an avid reptile keeper in the Chicagoland area. She stays involved in the Chicago Herpetological Society and has had writings published in the CHS Bulletin. She has done educational presentations for local grade schools and exhibited at North America's largest educational reptile show, ReptileFest, held in Chicago during April each year. She is a wife and mother and has been a nature enthusiast since the age of 7, when she spied her first coral snake in a pine forest of the southern U.S.

Why build your own snake or other reptile cage?

When I first started my interest in reptiles I was only young. At that stage of my life I had little or no skills and did not understand the requirements of the wonderful creatures so I did not keep them effectively. We just kept the local lizards, so the cage temperature was not an issue.

I rekindled my desire later in life but I also had mortgages, the cost of raising a family and the daily costs of living to contend with. A reptile was expensive enough, without adding the costs of retail cages and accessories. So I built my own. It saved me a lot of money.

You do need some basic tools but the money you save by making it yourself will allow you to purchase some of those tools that help make the cage. The remainder can go into accessories so that for the cost of a basic cage with nothing else you can make a cage, get some tools and the cage accessories and still have money left over. That’s a big difference.

Many people have materials about the house. If you are going to make your own cages you can save even more money by using bits and pieces or timber you may already have, screws, old glass, hinges, light battens etc. that you already have in the basement or garage.

When upgrading one of my cages recently, I was able to reuse some of the materials and the fittings for use on the new cage. This saved me having to purchase new accessories and materials.

Another benefit is the ability to maintain your own cages. Many of the plastic or moulded cages cannot be fixed once they are broken. With a cage you made yourself you can usually fix broken locks or replace doors (I haven’t had to do any of these yet as they are very sturdy).

When you build your own cages you decide how strong it will be and what quality of fitting, glues and materials you will be using. The higher the quality of materials and accessories you use, the better the final cage product. You are not at the mercy of manufacturers saving money by using inferior materials and poor quality fittings.

Another benefit is the ability to customise you cages to suit your purpose. One of my earliest cages was built as a normal cage but by placing a removable divider in the middle it allowed me to re-use the cage when I shipped one of the snakes out. This divider was fitted over the middle of a heat mat, allowing for two reptiles to be housed in the cage. It also had two doors. The cage is now used for another purpose but will soon be empty. The divider can still be placed back in the cage for another small snake and then simply removed as the snake gets larger. Tis snake will finally be moved into an arboreal cage. To purchase a plastic cage with divider that will only be a transient cage before the snake goes into a final cage is an expensive exercise.

If you do need to upgrade again, you have the time to build the final cage as the snake grows.

Making your own cages allows you to build and maintain your reptile cages in a cost effective manner while keeping them comfortable and healthy. You can also expand your collection in an affordable way, making more money available for the reptiles while still getting quality cages.


Feedback and Updating

A minor review of the "How to build reptile enclosures" book was completed recently and the new book is uploaded.

Those of you who have purchased the book can download this newer version and any further updates as they occur free of charge and they will open automatically. If you have lost the download details, just email me and I will send them out to you.

I have added:
- How to make sliding doors
- Better waterproofing your cage
- Making artificial trees (also added to the site at
- A number of minor amendments and additions

I would appreciate any feedback, good and bad about making your own reptile cages. I am looking for information, constructive criticism and ideas. These could include things like:

- What sort of additions would you like to see made eg making vivariums, wooden cages for Iguanas, making a cage stand etc ?
- How could the reptile cages be improved further?
- What are you particularly proud of?
- What worked well for you?
- What did not work well?
- What was difficult and how you got around it
- Requests and ideas for future reptile cage plans eg "How to make a reptile cage stand"

In particular I will soon be documenting the arboreal cage building process but I do intend to review as much as possible, hopefully based on user feedback as much as anything else.

I would also appreciate any pictures you have of your cages - using my plans or otherwise (we're all in this for fun and enjoyment so share away), so we can start to build a gallery of snake, iguana and other reptile cages of different varieties. This would be particularly useful as while many people like to show their pets in photos, not many pictures show the enclosures and I know that many people are interested in seeing how others have set up their reptile cages in order to get ideas.

I believe the collective pool of knowledge and skills we have can allow these plans to improve on a continuous basis.

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IGUANA CAGE PLANS has launched

The feedback on these plans has been very positive. Made by a recognized iguana cage maker with many years experience and a wealth of knowledge about keeping Iguanas. These cages are fabulous and could be easily adapted to large snakes and large lizards or arboreal species.

When you purchase reptile cage plans you also get access to a copy of these plans as part of your purchase. They can be used for large lizards and large snakes quite easily, but you do need some room to put them in as they are quite large

They are easy to make and it does take a little time. But you get a great cage in return. You can alter the cage to suit your own personal style and there are hints and tips throughout the book.

If you have already purchased reptile cage plans you can collect you copy of this eBook for free. Simply email me and let me know you would like a copy and I will send you a username and password so you can download your own copy.

Otherwise, go and make a purchase now and get a copy of this fantastic resource as well as the original plans plus all of the great bonuses. You will not find a better deal anywhere.

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We are always on the lookout for content, stories and feedback on what you think of this (or any other) issue of Keeping Reptiles.

And of course, if you have any suggestions for upcoming issues that you'd like to share with us, please send those, too!

These could include:

  • Great herp web-sites
  • Why you pet reptile is fantastic
  • Funny things that happened
  • Dumb**s things that happened (like the one in the previous issue)
  • Tips you have learnt
  • Things you are doing that may be of interest to others
  • Images you'd like to share.

Remember - there are lots of people who would love to hear your stories. Just e-mail me at: Reptile-Cage-Plans

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