Indoor Lighting for Tortoise Keepers

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Oct 7, 2010
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*Disclaimer* I’m not a scientist, doctor, vet, electrical engineer, or anything else truly qualified to author something as important as this, so don’t take it as gospel. I’m an Electrician with a keen interest in the subject matter, and a layman’s experience in applying the science of light. Everyone has a different situation to deal with, and as much as I would like this to be a one-size-fits-all approach, you still may need to apply some further effort to optimize your setup. I’m certain many highly experienced keepers may disagree with my opinions, and that’s fine. Hopefully by the end of this article you’ll be able to make an informed decision on your own.

I’ve seen a considerable amount of confusion in the tortoise community about how to properly provide indoor light to our companions. Much of this confusion stems from the marketing techniques of the industry coupled with a lack of understanding of the nature of light on the part of consumers.

For those of you that want the answers without having to read all the blah,blah,blah, here you go.

Go to your local hardware store and buy Full-Spectrum T-12 (the old-fashioned ones that have 1 1/2” diameter tubes) fluorescent lamps. They can be found with various names: Daylight Deluxe, Chroma50, Chroma75, DSGN50, Sunstick, Sunshine, Colortone50, etc.. These will always have a CRI (Color Rendering Index) of 84 or greater and a Lumens rating of around 2000. Any lamp with a rating approaching 3000 Lumens is a “fake” and not truly Full-Spectrum (From my experience at the time of this writing). Forget about the more modern T-8 and T-5 (1 inch and 5/8 inch respectively) as none that
I’ve tested so far have proven to be Full-Spectrum, despite what the box claims. (Except in the case of some of the shorter versions, 18 inch and 2 foot, etc, which may be an option for very small enclosures, but these small lamps actually cost more than the four foot versions.)

You should be able to buy some nice “shoplights” at the hardware store to mount your new lamps in if you do not already own some. Corded versions of high enough wattage rating are becoming harder to come by, but are still available. In a pinch, 40 Watt T-12 lamps will work in Electronically Ballasted T-8 Fixtures from my experience, but intensity and longevity will suffer. If corded versions cannot be sourced, it really isn’t that tough to attach a cord, and all the parts needed to do so ARE available at hardware stores.

These “old-fashioned” lights are favorites among fish-keepers, indoor-gardeners (aquatic, terrestrial, and nefarious), bird-keepers, and artists for the same reasons they are ideal for reptile-keeping. They produce a reasonable approximation of natural sunlight at an affordable price. (around $2.50+ a lamp, much better than the $20+ for “reptile” lamps). In regards to how many lamps one should employ, the easy answer would be to get as many as you can physically fit over the enclosure.

Traditionally, indoor housing for reptiles is FAR dimmer than actual sunlight, even on an overcast day, which may account for the “depressed” nature of many indoor kept animals, they can get SAD (Seasonal Effective Disorder) just like you or I. A typical indoor garden may very well have 4 lamps placed 6 inches away from a 2 foot by 4 foot planter. The undeniable advantage that comes with bright illumination can be, as an example, the ultimate rain-forest re-creation. Full sunlight filtered through a vegetative canopy is virtually impossible to synthesize with lighting alone, but add an actual vegetative canopy to your enclosure, and you're there.

Contrary to popular belief, these lamps also produce significant quantities of UVA and UVB radiation, it is however, normally filtered out by lenses, or made negligible by distance, for human safety. Most should be the approximate equivalent of a 2.0 Reptile Lamp, which implies then, that four used with quality reflectors at a 12” distance should suffice to meet the UVB requirements of Forest Species, and 8 or more for Desert. Seems like a lot of lights and really bright, doesn’t it? That’s sunshine. This would also be a safer approach than the typical Reptile Lamp, as the radiation would be a little more diffuse, and the illumination level to UV radiation level would be more in line with natural sunlight (around 10 visible to 1 UVA to 1/10 UVB, depending on location and time of year) allowing the reptiles pupil to dilate to the correct “openness” to avoid letting in too much ultra violet and damaging the retina. As many experienced keepers have had issues with animals suffering from MBD (Metabolic Bone Disease) even with correctly installed reptile lights, more testing will be needed to see if this method will prove adequate. I suspect that many other factors come into play, and we're still on the forefront of understanding UVB and D3 production. I can’t stress enough that this is all based on theory, and not thoroughly tested. In all honesty, regardless of how we are trying to meet UVB requirements an UV Meter is needed, and even then we don’t truly know how much they need. The best bet is still to get them as much natural sunlight as possible.

A high heat basking spot is still always needed, which makes for a good opportunity to ensure adequate UVB if uncertain, with the use of Mercury Vapor UVB lamps or Halogen/Incandescent Spot lamps combined with Reptile Fluorescents. With all of these solutions please do understand, that they should all be equally safe and effective IF the manufacturer is a “quality” one and their directions are followed EXACTLY. Many studies indicate that D3 production is increased with an increase in skin temperature, making basking the ideal time to apply UVB radiation. I SUSPECT that many failures in the past with UVB lamps for reptiles can be traced to both inadequate instructions from the manufacturer and quality control, both failings they have been striving to correct. (Open package. Install. Enjoy :) doesn't really qualify as GOOD instructions now does it?) Other possible failure mechanisms could be keeper expectations, as an 18 watt reptile lamp in a 2 foot by 4 foot enclosure placed in a location the animal seldom frequents for an extended period of time will do little good. These types of lamps DO NOT however, produce an adequate Full-Spectrum of light to meet the vision requirements of reptiles.

In the case of smaller enclosures, a basking light may be all that is needed in the way of illumination, as for the most part, these enclosures are used only for housing babies. MVB lamps are deficient in the blue part of the spectrum, so could possibly be augmented with an aquarium actinic lamp. A more practical approach may be to employ the dreaded belly-heat (heating pads, ropes, etc) in conjunction with a CFL UVB Fluorescent. These have a bad reputation for producing too much UV, but this issue has been largely addressed by the manufacturers. They do in fact seem to produce a fuller overall spectrum than most other reptile lamps available. Options abound, and opinions are more plentiful yet.

Now for a little more of the “science”, hopefully explained in a way that the majority can understand. I’ll try to keep the techno-babble to a minimum.

Just like your car radio has different frequencies that you can tune into to change the station, animals that see color can tune into different frequencies of light. Inside our eyes are little receptors, called cones. As it turns out, Reptile eyes are different from human- they have 4 kinds of cones to see colors while we only have 3. . This means that while it only takes 3 colors of paint or light to mix every color we can see, reptiles require 4. The 4th cone in reptiles receives UVA radiation! They SEE UV. Leaving out the UV element for a reptile would be like leaving the blue out of a human’s world. Food, potential mates, your surroundings- everything would look strange if a whole color was left out or dimmed. Mammals may have sacrificed this 4th color for better acuity or distance vision, but we are still affected by UV in other ways, as are reptiles. The pineal gland responds to UV and helps set our sleep patterns, growth, and seasonal functions. UV also causes complicated reactions in the skin- good and bad- from D3 production to tanning, cancer, excema, and so on. As we have no way of knowing how much UVA the reptile needs to see the world correctly, we can only strive to reproduce nature, wherein UVA usually makes up 1/10 of the overall visible light.

Its an easy experiment to examine the wavelengths (ie. colors) aside from UV produced by a light source. If you take a CD or DVD and hold it underneath a light source, you can see a rainbow. That rainbow represents the “broken down” components that make up that beam of light.

Here Is an Example of Natural Fall Sunlight Through a Window of My Home


Here are two fluorescents
a Chroma50


A Cool White T-5 (ie. modern)


You’ll notice that although the Chroma50 falls short of the range of color found in “fall sunlight through a window of my home” it does have more of “blending” of shades between colors than the T-5, which has little to no blending, the red band is of entirely one shade of red, etc. This has to do with the phosphors used in making the lamp. Halo-Phosphors are old technology, and produce light across a wide spectrum. Newer lamps use “Tri-Color” phosphors, which produce intense light in narrow color bands. This is where the great efficiency of the newer lamps comes from. We perceive the light as brighter than it actually is. Its great for lighting our homes and workplaces, but fails to produce all the necessary wavelengths to sustain “life” or make our reptiles happy, as they see light in a different way.

A simple spectro-scope can be made with a cd or dvd and a cardboard box to make viewing and evaluating easier for the curious. A quick search on google will find many other similar plans.

More Advanced Ideas:

Ideally we want to recreate an entire day for our companions, dawn to dusk. Not only is it rather rude to blast our poor Torts with noonday sun when they were resting quietly in the dark, but by recreating the subtle light changes that occur throughout the passage of the day we can give them a sense of time of day to entice natural behavior and make them feel more at home. Timers are useful for this. Timer power strips can be purchased from the pet store, or plug-in varieties from the hardware store. For those knowledgeable in safe wiring practices, in-wall timers that can mount in an electrical box can provide a nice solution. Digital timers are more convenient and elegant, but I have run across a few that won’t operate fluorescents.

Very early morning, late evening and deep shade tends to be characterized by blue light. This kind of light is considered “cool” and represented by color temperatures of 10,000 Kelvin or greater . (Color Temperature is the industry’s way of categorizing the balance of light color of a lamp as perceived by the human eye). Actinic aquarium lamps produce blue and violet light (and likely considerable UV A and B). This also conveniently happens to be the “weak area” of most common reptile lamps (except of course for the UV).

Later In the morning, as the sun starts to peak over the horizon, the light “warms up” with more red light. Warm light is considered low on the scale, 1000-3000 Kelvin. Incandescent and Halogen lights work great for this as they produce primarily in the red part of the visible light spectrum. They also produce a lot of heat to help warm the enclosure if needed.

As mid-day approaches yellows and greens begin to predominate, giving sunlight the “brightness” we associate with that time of day. This kind of light is considered 5000-7000 Kelvin.

An Example Lighting Schedule Idea;
7 AM Actinic Aquarium Fluorescent
8 AM Standard Incandescent Lamps
9 AM Reptile UVB Lamps
10 AM Daylight Lamps

And then of course reverse the other way a few hours later.

This kind of set-up would not only provide the animal with a shifting color temperature and brightness throughout the day, but the given lamp types can augment each other’s weaknesses to provide true Full-Spectrum light at ratios comparable to natural sunlight for our reptiles. In closing, I repeat this is not gospel. Many Tortoises have been succesfully raised before this was written, and I'm sure many will be raised without following anything I've stated here. At the least I hope this can help other keepers to better understand their tortoise companion's needs, and make better, more informed purchasing decisions. There may be errors present, and new knowledge unfolding, and hopefully a better guide to follow in the future.

Further Reading and the sources of much of the knowledge presented in this article.
*This is obviously geared towards aquatics, but has a TON of information about lighting that is pertinent to tortoise keeping. A commercial site, so take suggestions with a grain of salt.*
*I decided to leave out a discussion of SPD graphs (Spectral Power Distribution) for now, but for the curious, they can be a handy tool for evaluating lighting sources.*

Actinic : Special Lamps used in photography and reef aquarium keeping, producing mostly blue light.

CRI (Color Rendering Index) : A rating scale of 1 to 99 for light sources in regards to how well the

human eye can distinguish the colors of objects illuminated by them. Higher = Better

Fixture : An object designed to hold, protect, and control the power of "lamps".

Fluorescent : Lightning in a Test Tube. Literally. Electrical current passing through mercury vapors generates ultra-violet radiation. Phosphors (special dirt) coating the inside of the glass tube react with that radiation and GLOW. Go a little skimpy on the phosphor coating and some of that UV gets out, and then you can charge more because its now a "Reptile Lamp" or a "Black Light". I've seriously wondered if that's why such a huge variability can be seen in actual UV production in reptile lamps. They just buy the defective ones that didn't get coated well. Technically a special glass is supposed to be used to allow more uv out, but do these bulbs actually have that glass?

Full-Spectrum : Makes ALL colors and shades of light.

Incandescent : Plain old Edison light bulb, with the hot-glowy wire in it.

Kelvin : Color Temperature. You'd think hotter would be redder right? Wrong LOL. It goes the other way, bigger the number, bluer the color, lower the number, redder. Lights designed to emulate mid-day sun are designed to produce 5000 K (Kelvin) light, which is presumed to be neutral.

Lamp : I don't mean that ugly thing on your night stand. That's a "fixture" (Electrician Terms). The Lamp is the glass thingy that makes the light.

Lumens : This is a funky one. Essentially it means how bright a light looks to the human eye, it does NOT actually indicate how much light is produced. A "plant" light for example produces most of its light in colors that appear "dim" to humans, so they typically have low lumen ratings, but they still produce just as much light energy as a "brighter" higher lumen lamp of the same size. That's why you
can use the Lumens number to evaluate "Full-Spectrum" lamps. A typical "modern" daylight lamp claims to be getting 3000 Lumens with 32 Watts of Energy, while older varieties get 2000 Lumens with
40 Watts of energy. Yes, the newer varieties have a slight benefit from smaller size, which increases intensity, but not enough to justify 50% more power from 20% less watts. (See why they sell so well? I fell for it for years, until it killed my plants after I "upgraded"). The difference is, the newer varieties don't "waste" all that power on colors you don't see well in addition to the Tri-Chromatic trick explained in the article.

Reptile Lamp : Special lamps sold to reptile keepers, Repti-Sun 10.0 , etc. See Fluorescent

T-Whatever (5,8,12) : This is a sizing designation for fluorescent lamps. The number refers to how many eigths of an inch the diameter of the tube is. T-5 = 5/8" , T-8 = 8/8 (1) ", T-12 = 12/8 (1 1/2) ".


Enjoy! :)

Balboa and Mark Adkins
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