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Iguana Lighting

How To Properly Light Your Iguana Enclosure

Iguana Lighting

Iguanas, like all living animals, require lighting in order to thrive. Iguanas utilize 2 forms of UV lighting, as do humans. There is UVA, which is essentially for the mood of your iguana and its general well-being. UVA is a visible spectrum of light that is produced from everyday household bulbs, fluorescents and even window lighting. There is also the UVB spectrum of light, which is as important, or more important for your iguana. UVB is the spectrum of light that will help keep your iguana alive and healthy.


Iguanas need a photo-period of 12 hours, which can be increased to 14 hours during the summer months. They will spend much of this time absorbing the suns rays or the UV bulb rays that you've supplied. This does not have to be the only source of light in the enclosure. By placing a 75-100 watt normal household bulb atop the enclosure, you will increase the total light in the enclosure and help to create a realistic simulation of actual, outdoor sunlight.

Vitamin D3

A major problem with keeping iguanas healthy in captivity, is supplying them with an appropriate supply of Vitamin D3. Vitamin D3 is a fat soluble vitamin that an iguana needs to assimilate the calcium in its diet. Without it, your iguana can contract a severe case of Metabolic Bone Disease.

There is no good source of this vitamin found within fruits and vegetables. It is also believed that iguanas can not absorb this vitamin through their food. So attempting to use a supplement is useless.

Wild iguanas manufacture their own vitamin D3 by basking in unfiltered sunlight. The ultraviolet radiation from the sun acts like a catalyst which converts a substance known as pro-vitamin D3 into pre-vitamin D3. In turn, this pre-vitamin D3 is converted into vitamin D3, which binds to a blood protein and then can be transferred to the liver via the bloodstream. This "activated" form of D3, then can be utilized to influence the metabolism of dietary calcium and phosphorus.

So how can you supply this crucial vitamin to your iguana? By purchasing the correct light. There are many "so called" reptile lights on the market. Many of them produce a spectrum of light known as UVA rays. Although UVA rays are good for increasing appetite, improving general fitness, and inducing reproductive behavior, they do not produce the vitamin D3. That can only be found in the rays referred to as UVB. The UVB rays found in the light you provide (or by access to one hour of unfiltered sunlight a day) are essential for the proper breakdown and utilization of calcium and phosphorus in your iguanas diet. Therefore, it should be considered a necessity when configuring your iguanas dietary needs.

UVB Solarmeter
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UVB Solarmeter

UVB Lighting

Iguanas that are allowed to bask in unfiltered sunlight for one hour per day will absorb enough UVB to utilize the calcium in their diet. UVB is filtered a short wavelength and is not very strong compared to UVA. Unfiltered means that there is no glass or mesh beyween the iguana and the sun. Placing your iguana in a window will NOT supply the UVB it requires. Placing your iguana in a mesh enclosure outside, which will filter most of the UVB will NOT supply your iguana with the UVB is requires. Any screening used must have openings that are at least 1/4" wide in order for UVB to reach your iguana. The bigger the openings you provide, the more UVB reaches your lizard. This seems to be a very common issue with new owners. Many are ignorant and believe that because the enclosure is near a window, the iguana is getting all that it needs. All the iguana is getting from that window is UVA lighting and it still won't be able to properly metabolize the calcium in its diet. When an iguana can't metabolize its dietary calcium, it pulls the calcium from its own body to supplement itself. This calcium is typically drawn from its own bones and this is what leads to the blanket illness known as Metabolic Bone Disease..

Outdoor enclosures, like the PVC Knockdown Cage, are ideal for allowing your iguana to bask outside, safely, to meet its UVB requirements. Many of us do not live in a climate where we can allow our iguanas the ability to bask on a daily basis due to temperatures outsides. These iguanas require us to provide artificial lighting in order to supplement them with their UVB.

There are 2 primary ways for us to supply UVB indoors. Both require the purchase of artificial lighting and both have specific situations where they should be used.

There are a number of manufacturers that provide UVB emitting fluorescent tube lights. These are specialty lights and are not the same as a normal fluorescent tube used in your office. They specifically state that they produce UVB and it is crucial that this is the type of light that you purchase. These lights have a fairly low UVB output and need to come within 6-8" of your iguana to be their most effective. These lights are normally used where a basking shelf is located and the light can be placed in close proximity to the animal. There can NOT be a glass or fine mesh barrier between the light and the iguana. You are simply wasting money and allowing your iguana to die a slow and painful death if you do this. You can't "see" UVB. Just because you see light (UVA), it doesn't mean your iguana is getting UVB. These lights do not typically last very long and should be replaced every 6 months to ensure they are still producing adequate UVB. Again, light DOES NOT indicate that the bulb is supplying UVB. It simply means it is producing UVA. It is very important that you understand this. In a perfect world every iguana owner would own a UVB Meter. This would allow you to measure and monitoring the output of UVB from whatever light you are providing.

I personally own and suggest a Solarmeter 6.2 to everyone who owns a basking species that requires UVB lighting. The Solarmeter 6.2 is not cheap but does its job with great precision and keeps you on point to when you need to replace your light. EVERY artificial light is going to need to be replaced as the UVB deteriorates over time. This is the ONLY way to know for 100% certain when this needs to be done. If you are going to care for exotics animals that require special lighting, be prepared and buy yourself a Solarmeter 6.2 and do it right.

Those with larger enclosures (I wish it were everyone reading this) will find that the fluorescent tubes aren't strong enough to supply UVB in their large enclosures. These enclosures tend to do much better while using Mercury Vapor bulbs. Mercury Vapor bulbs produce a much higher spectrum of UVB at a stronger intensity. many of these bulbs come with minimum distance warnings on them. This is to ensure that people with shallow tanks are not slowly cooking their animals. These lights screw into normal looking sockets, like an ordinary household bulb would, except the socket should be made of porcelain and not plastic. These lights can produce great amounts of heat and can melt plastic sockets. Porcelain sockets are very easy to come by. they are sold at all home improvement stores.

There are 2 types of MV bulbs on the market. Both of them require a ballast to function (it comes with or part of the light). One of them is the external ballast MV. The other, naturally, is an internal ballast MV.

The internal ballast MV are the more popular of the 2 types because they can be purchased readily online, as well as in the petstore. These lights produce both heat and UVB, making them popular among hobbyists. These lights get very hot, which makes their filament brittle when on. Since these lights get this hot, they can not be moved while they are on or the light may fail. You never want to touch or move an internal ballast light when it hasn't been cooled first. You ARE going to burn yourself and the likelihood that your light will break is high. You also need to ensure that your iguana can not touch this light. I can't say it enough, this light gets hot! It WILL burn your iguana. You can place it out of the iguanas reach or you can take preventative measures and encase it in a Heating Element Enclosure.

Externally ballasted bulbs are popular but more difficult to find. I have yet to find an externally ballasted MV light at a normal petstore. These lights, unlike the internally ballasted lights, do not emit much heat at all. I still don't advise moving this light while it is on but the lack of generated heat reduces how brittle the filament is. These lights have a box that the light plugs in to. The box is called the ballast and it can become warm, though my experience hasn't been warm enough to cause burns. Since this light doesn't create heat, it is a necessity that you provide an external heat source in tandem with using this light to create a proper basking zone.

Whenever possible you do not want to have ANY barrier between your light and animal. Anything between the iguana and light source is going to reduce the UVB that is reaching your animal.

Basking Zone

Iguanas require a basking zone. Normally the basking zone is the highest point that the iguana can reach in his or her enclosure. It is no closer than 6-8 inches and no less than 12 inches to the lighting and heating fixtures and is very stable. (The distance will be determined by the temperature and UV checks you do.) The size of the basking zone depends upon the size of your iguana. It should be large enough that your iguana can stretch out and soak his or her entire body under the heating and lighting fixtures. This is where your iguana will spend most of its time and this is where the primary ultraviolet lights (UVB emitting) should be set. You should place a digital thermometer (with probe) within the enclosure around the basking zone and maintain the ambient temperature around 90°-95° F. Exceeding these temps could cause the enclosure to dry out rapidly. The thermometer and temp gun above are the tools I use to maintain my reptile enclosure temperatures.

The basking zone temperature, or the surface temperature of the iguana laying in the basking zone, should be maintained between 100° and 110°. These temperatures should be measured using a temperature gun. Temperatures in the basking zone need to be measured from the animals body and not by the shelf they will be laying on. The temperature could be perfect on the shelf but could be substantially hotter on the iguanas back, since the animal is made of mass and will be physically closer to the element that what the shelf is.

Reptile Lighting

Understanding the role that lighting plays in your reptiles life is crucial to providing it with the best living conditions. Frances Baines, M.A., VETMB, MRCVS, wrote a magnificent piece on Reptile Lighting that was featured in Reptiles Magazine. With her permission we have the article posted on the site for everyone to learn from. Please take a moment to read and understand the information that she has provided since it is detrimental to the success or failure you may experience with your reptiles.

Reptile Lighting by Frances M. Baines, M.A., VETMB, MRCVS


Author: Richard Brooks
Reptile Lighting © Frances M. Baines, M.A., VETMB, MRCVS
UV Guide