Lighting - Leopard Gecko
As you should already be aware, leopard geckos are nocturnal. This means that they are primarily active when the sun has already set or right before it rises. As an owner, this is great for you. Unlike basking species, they don't require the expensive UV lighting that some species need. They do however require a photoperiod like other animals.
A photoperiod is a cycle of light, and a cycle of darkness. The typical photoperiod is 12 hours of light and 12 hours of darkness. During the summer months, to replicate seasons, lighting can be done in the cycle of 14 hours of light and 10 hours of darkness. It is detrimental to all animals that a proper photoperiod transpire.
The simplest way to light a leopard geckos enclosure is with a normal household bulb. A low wattage (as to not disrupt the temperature gradient you should have created) bulb would be sufficient. Try to set a normal routine and turn the light on and off at the same time each day. To simplify your life, and to ensure you are providing a normal routine for your gecko, you should invest in a timer. Most hardware stores carrying as do various retail outlets. The timers typically have two settings that you adjust. The first is the on time, and the other is the off time. These timers can be purchased for really cheap money and will ensure you have created a proper photoperiod for your leopard gecko.
Some enthusiasts do not use any additional lighting on their enclosures. This is only an option though when the room they are being kept in is brightly lit for a specified number of hours each day. If the room you house your leopard gecko in is not brightly lit each day, you should be providing another means of ambient light.
Ultraviolet Lighting - Leopard Geckos
Petstores are notorious for suckering new enthusiasts into buying an expensive UV light for their leopard gecko. They claim the leopard gecko needs this lighting to create D3 in order to metabolize the calcium in their diet. While this is true for diurnal basking species, it is an outright lie when referring to leopard geckos. Leopard geckos are nocturnal. They do not come out and bask in the sun in the wild like iguanas and other species do. In fact, bright lights hurt their eyes. Further more, UV lighting, when constant exposure is present, can actually cause blindness in leopard geckos. It is not needed, not safe for use, and certainly not worth the money they are trying to get you to spend. If you are currently using a UV light to create a photoperiod for your leopard gecko, please stop. The only time a UV light should ever be used with leopard geckos is when they are being treated for Metabolic bone disease. In those rare instances, the light should be limited to 3 hours in the am each day until improvement is present.