A chameleon needs UV light to be able to use the calcium that’s in its food. Especially UV-B light is important. When UV-B light falls on the skin of a chameleon, it will produce vitamin D. In humans it works the same way. Vitamin D is crucial for absorbing calcium from food in the intestines. When a chameleon does not absorb enough calcium a chameleon can develop abnormalities in bone growth, rachitis, Metabolic Bone Disease (MBD) or just get very weak bones that are prone to breaking. UV light is also important for the general well-being of a chameleon and to help it show beautiful colors.
You only need to provide UV light during the day, for around 10 to 12 hours. One UV light in the entire terrarium is enough.
A good UV lamp
In nature a chameleon gets its UV light from the sun. In captivity we can provide UV light from a lamp. You can choose between a compact light bulb (CFL) or a standard fluorescent tube. There are many brands and types of UV lights for sale for reptiles, but not all of them are suitable for chameleons. It is important that the light bulb is strong enough and emits enough UV-B light consistently. The UV lights also emit normal visible light but emit very little heat.
A good lamp for a chameleon is the ZooMed ReptiSun UV-B 5.0 or ReptiSun 10.0 linear or compact fluorescent lamp. The ReptiSun 5.0 compact can be screwed into any normal large fitting. Other good brands are Arcadia 6% or 12% and ReptiGlo 10.0. A light that will both provide heat and UV light is the ZooMed PowerSun.
You have to replace the light every year because the UV-B yield goes down when the lamp gets older. Please check some reviews of chameleon breeders if you are looking into buying a UV light. They can tell you about the good and the bad brands so you can buy a good one for your chameleon.
Positioning the lamp
It is very important that the UV light is in a good spot for your chameleon. Place it somewhere where the chameleon can never touch it, it should be able to get as close as 1 foot (30 cm) but not closer. A central place at the top of the terrarium is best. If possible you should allow the chameleon to choose how close it will be to the UV light and how close to the heating. It should be able to find a spot with a good temperature and still receive UV light. In that way it can regulate itself a bit.
UV lights could cause eye problems in reptiles. Make sure you have a proper brand of light bulb and make sure the chameleon can find a spot where it does not need to look into the light all the time.
Natural sunlight
Unfiltered sunlight also has a lot of UV-B. It is very healthy for your chameleon to be allowed to bask in it, but make sure it can hide in shade and can cool off. The outside temperature should not be lower than around 20 degrees Celsius (32° F) as your pet chameleon will be used to high temperatures inside its terrarium.
UV light does not go through glass or plastic, so you need to place a net cage directly in sunlight to have the UV benefits for your chameleon. If you are continually supervising, you could also bring out branches or a potted plant with the chameleon to allow it to sit in the sun in the open. Twenty minutes a day of unfiltered sunlight will do wonders for your chameleon. Do not let it stay out for hours when it is not used to it, try to start slowly and don’t overdo it. When your chameleon is used to the sun it will move to the shade when necessary. When it’s hot and dry, spray the plants or fake plants with water to increase the local air humidity and allow the chameleon to drink.