UV lights or ultraviolet lights are very important for turtles and tortoises. Without the exposure to that form of radiation, they are unable to synthesize vitamin D, and they do not have a normal calcium metabolism. This can lead to all sorts of illnesses, and it's unfortunately one of the most common things we see at my practice. So, ultraviolet lights, again, if you're housing your turtle outdoors, you don't need a special light because the sun will do that work for you. But the lights that we have available to us for housing turtles indoors, the two most common kinds are fluorescent types of lights and mercury vapor types of lights.
So fluorescent lights either come in a compact or coiled looking form, or they can be a long tube fluorescent bulb. They do produce a good amount of ultraviolet light, but again the distance from the turtle is important. If you're more than two feet away from the pet with the light, they probably won't be getting a whole lot of exposure to those beneficial rays. Fluorescent lights also do not put off any heat. So, again, most reptiles need a basking area, and it's very important that you have an additional light or heat source when you're using a fluorescent UVB bulb.
Mercury vapor bulbs are large round bulbs. They produce ultraviolet radiation and heat. So, again, you can simplify your setup sometime by using these bulbs. Again, you want to be sure the temperatures are appropriate. Not too hot and not too cold under that bulb, and make sure it's not too far away from the animal so that they are getting ultraviolet rays.
You can purchase these bulbs at pet stores that sell reptile supplies. But again, don't confuse them with bulbs that say they're full spectrum or UVA basking bulbs. Those bulbs do not contain UVB. UVB is really the thing that you're looking for when you're choosing the bulb. Bulbs that have the UVB light generally are more expensive than just your regular incandescent basking bulbs. If you can't find a UVB bulb at your local pet store, there are many places you can go online these days and order them. So, again, any turtle or tortoise's tank or enclosure is not complete without a source of UV light. It's very important that you supply your turtle or tortoise with that light or they can become ill.