The best light for your turtle is direct sunlight, of course! But it is not always possible or safe to keep your turtle outside year-round. If you, like so many turtle owners, must keep your turtle indoors, it is imperative that you provide proper lighting so that your turtle's psychological and physical needs will be met.
To replicate sunlight, you will need to provide UVB light, UVA light, and heat. Of course, visual light is needed too! All of this can be provided with only two lights, a UVB light and some kind of light for heat. In the case of mercury vapor bulbs, one light does it all! We'll also explain why each of these are so necessary. It is not possible to replicate this by placing your turtle near a window! Much of the required rays will be filtered by your window and the aquarium glass!
It is important when selecting a UV bulb for your turtle's habitat, that you are mindful that most UVB lighting begins to lose potency after about six months (despite what the package says). The exceptions are the ReptiSun 10.0 and mercury vapor bulbs; each of these produce viable UVB for up to one year.
UVB does not penetrate more than a few inches below the surface of the water, so be sure to position it directly over your turtle's basking area. If you are using an aquarium hood, remove the plastic or glass that covers the light strip, as it will filter out almost all of the useful UVB rays. The UVB rays are also blocked by fine mesh, so mesh should be at least 1/4 inch diameter.
Importance of UVB
To meet their dietary and metabolic needs, it is crucial that most reptiles are provided with high quality lighting. UVB light is needed for animals to produce vitamin D3. This vitamin is necessary to process calcium. The absence of vitamin D3 will prevent the metabolism of calcium which can quickly lead to a condition known as Metabolic Bone Disease (MBD).
MBD is the number one killer of captive tortoises, turtles, and lizards. It is especially a risk for egg-laying females and fast growing hatchlings since they need even more calcium than other turtles. The condition is a result of the suffering of bone density, and symptoms include lethargy, swelling, weakness, and tremors. In addition, turtles' shells may become soft and pliable.
UVA is the "feel good" light. It encourages your turtle to bask and enjoy the sunshine, and it may have good psychological properties for turtles. This is the same reason why it feels so good when you take a nap in the sunshine! Luckily, any UVB light will also have UVA.
This brings us to the next important component in the lighting of your turtle's enclosure: heat. The temperature of the basking area should be around ten degrees warmer than the temperature of the water. If it is not, your turtle might not bask. A flourescent UVB bulb will not provide sufficient heat for a basking area, so you will need an additional heat light or a heat emitter. This is easily accomplished and it is not necessary to buy a special "reptile bulb" for this purpose. A regular household bulb will do. Be sure to monitor the distance of the bulb from the basking area until you have reached an ideal temperature. Remember that as the seasons change, you might need to adjust the distance of the heat source from the basking area, or change the wattage of the bulb to compensate. The heat source will make it possible for your turtle to thermoregulate and properly digest its food. It will also dry your turtle's shell, preventing fungal infections and shell rot.
The Basking Area
Your turtle needs a basking area where he can get completely out of the water to dry off. A good basking area will be textured so that water can run off. The UVB bulb should be within 12 inches of the basking area, and the heat lamp should be at a distance to provide the correct temperature. The lights should not be blocked by glass, plastic, or mesh under 1/4 inch diameter.
Your turtle does not need a light at night, or a heat lamp. It's best to turn off your lights at night, or put them on a timer so they go off automatically. If you like to look into the habitat at night, we recommend using a light that simulates moonlight (soft blue) rather than a red heat lamp.
Also make sure that your turtle does get 10 hours of darkness. This can be difficult indoors, but your turtle needs to sleep too and doesn't have covers to hide under when the sun comes up at 6! Try to locate your turtle in a room that will stay dark after 10 pm.
Not providing these conditions can lead to many illnesses including soft shell and metabolic bone disease.