Using appropriate lighting is absolutely critical to your chameleon’s long term health. With all the different types of lightbulbs available at petstores it is easy to get confused about what you actually need. Here are the basics:
UVB light is the most important aspect of lighting for indoor captive chameleons. Ultraviolet light rays are emitted by the sun in UVA, UVB and UVC frequencies. UVB is invisible but critical to the formation of vitamin D3 in the skin of reptiles, which allows them to absorb calcium from their food. Chameleons must have UVB light to survive. Lack of UVB will lead to Metabolic Bone Disease (see health section), severe deformation, and eventual death. UVB can be given through unfiltered sunlight (UVB does not penetrate glass or plastic well) or through commercially available fluorescent UVB bulbs. After about 6 months of use these bulbs will stop emitting adequate levels of UVB, even though they are still shining, so it's important to change the bulb every 6 months or use a UV index meter to monitor for appropriate output.
Some suggested brands: Reptisun 5.0 or 10.0, Reptiglo 5.0 or 10.0, Arcadia 6% or 12%.
The basking bulb
A basking bulb is any light bulb that generates heat to create a warm spot at the top of the cage. Reptiles are ectotherms (cold-blooded), meaning they need to absorb heat from their environment to regulate their own body heat since they cannot produce it. Therefore a temperature gradient in their cage is essential to good health. They need a warm place to bask in order to digest food properly but they also need cooler places to cool down so they do not overheat since they can’t sweat or pant. A basking bulb provides warmer temperatures at the top of the cage but should not be so hot that it heats the entire cage. Your chameleon will utilize different temperature zones throughout the day depending on its metabolism and needs.
Linear Florescent UVB
These bulbs are the shape of long tubes. They are very popular since they cover a larger area and are very safe to use. They require a special fixture and generate very little heat.
Compact Florescent Light (CFL) UVB
These bulbs are the short and coiled and fit into regular light sockets. The Reptisun CFLs (not Reptiglo) were at one time associated with eye problems due to a manufacturing defect. This problem was corrected several years ago and CFLs are now considered safe. They generate little heat.
Mercury Vapor/ Metal Halide UVB
These specific bulbs are only stable at high wattages and thus put off too much heat and light for typical enclosures and should only be used in very large free range settings (10’x10’ or larger). These bulbs may require special fixtures and are much more expensive than other UVB options.
These bulbs are normal shaped incandscents and do not have UVB. They are used to create heat for reptiles to bask in for proper digestion and visible light. The wattage corresponds to the amount of heat and light (higher wattage = more heat). Generally a 40 or 60 watt bulb is appropriate. It should be a white light bulb.
Chameleons do not need night lights. A drop in temperature down to 60F (15C) is actually good for metabolism. If temperatures drop lower than that a ceramic heat emitter that does not give off light can be used. Chameleons have a photoreceptive scale (parietal eye) on their head that senses light so even the blue and red bulbs disrupt sleep.
Q: What does the number on the UVB bulb mean?
A: The numbers on the UVB bulbs corresponds to the percentage of light that is UVB. 2.0 bulbs are designed for reptiles that receive little UVB, such as those in the lower layers of thick forests where sun doesn’t penetrate well. 5.0 bulbs are designed for reptiles that receive moderate amounts of sunlight like those in the upper levels of forests that get dappled sunlight throughout the day, like chameleons. 10.0 bulbs are designed for animals that receive high levels of unfiltered sunlight for most of the day. Either a 5.0 or 10.0 can be used for chameleons but a 2.0 is not enough.
Q: Do I still need a special UVB bulb if my chameleon's cage is next to the window so it's getting real sun?
A: Regular glass blocks over 98% of UVB rays (which is why you don't get sunburned sitting by the window) so sitting your chameleon by the window does not provide any UVB rays unless it is open and there is no glass between the sunlight and your chameleon. The heat from the sun through a window can actually be a danger to your chameleon. A UVB bulb is necessary if unfiltered sunlight cannot be provided for 5-8 hours every day.
Q: The light hood came with a plastic cover. Should I keep it on or remove it?
A: Plastic will block the majority of the UVB rays so any plastic or glass cover should be permanently removed from the light fixture before use.
Q: If the UVB lights mimic the sun for my chameleon, are they also really good for plants in its cage?
A: While some plants can grow well under the UVB and basking bulbs of your chameleon alone, the UVB bulbs are low intensity and many plants will do much better with a light better suited for plant growth. These are labeled 6000k - 6500k for the color spectrum they emit, rather than a particular type of ray like UVB, and are higher intensity for plant growth. They can be purchased from most home improvement stores.