The lighting in a turtle habitat is very important. The lights aren't just there so we can see our turtles. It's much more important than that. In fact, your turtle's life depends on having the right kind of lighting.
Before we talk about your turtle's lighting needs, however, there are a few safety-related things I need to tell you that have to do with protecting people's health.
First of all, it is very, very important that you never look directly at a turtle light. They are very bright and can damage your eyes. The lamps that produce UV light are even more dangerous. They can cause blindness if you stare at them long enough. So never look directly at a turtle light of any kind, and don't aim them in such a way that people sitting in the room can see the bulbs or tubes or the glare from the reflectors. This is very important.
Secondly, you should always secure the lights over your turtle tank in such a way that they can't fall into the water. If they do, you or your turtles could be electrocuted. So if you set them on the screen cover, also secure them in some way so they can't fall into the water if the cover is removed. The way I usually do it is by hanging them from a wooden light bar and wrapping the wire around itself, then securing it with a zip tie or by wrapping electrical tape around the wire where it is looped over itself. You can see what I mean in the picture in the section farther down on this page.
Finally, never work with turtle lights (or other electrical accessories for your turtle habitat) with the power on. Electricity and water don't mix.
Now that we understand the safety rules, let's get back to our turtles' lighting needs.
Like all reptiles, aquatic and semi-aquatic turtles need three kinds of light, all of which should be pointed at their basking area. They need light that approximates normal sunlight, UVA (Ultraviolet A) light, and UVB (Ultraviolet B) light. They also need warmth like the sun would provide if they were living in the wild.
In nature, aquatic turtles spend a good part of every day basking in the sunlight. The warmth helps raise their body temperatures to help fight germs; and the daylight-spectrum and UVA light are important to activity, mood, feeding, and breeding. The UVB light is essential to Vitamin D3 production, which is vital for proper shell and bone growth. Without the proper lighting, our turtles will get sick and most likely will die long, slow, painful deaths from metabolic bone disease. UVB light really that important to turtles.
Turtles also need to have a basis for their circadian rhythms, which means that they need days and nights just like people do. Without day and night cycles, your turtle's sleep habits will be disrupted, causing stress and reducing your turtle's immunity and overall health. As your turtle's keeper, you are responsible for creating everything in their world --even days and nights. You use the lights to do this.
Let's talk a bit more about UVB light because it's something that a lot of new turtle keepers have a hard time understanding.
Turtles (and all reptiles) need UVB light to produce Vitamin D3 and to help them properly use calcium and other nutrients. Without enough UVB light, turtles will experience shell problems and metabolic bone disease. If they are deprived of UVB light for too long a time, they will die. So please be sure that you can afford to buy a UVB lamp and replace it every six months or so before you get your turtle.
I say this because many captive turtles don't have enough UVB light simply because their keepers simply can't afford one. This is especially true when people get baby turtles at a carnival or a fair without planning for them in advance. Many of these baby turtles will die in less than a year because their owners simply didn't know how to take care of them until after they had the turtle.
It's not always the keepers' fault, though. Sometimes people who work in pet shops don't know a lot about reptiles and they sell the keepers the wrong lights. Just because a light bulb says "full spectrum" or "sun spectrum" on the package doesn't mean that it produces UVA or UVB light. In fact, most "sun spectrum: lamps provide very little, if any, UVA or UVB light.
Unfortunately, many new turtle keepers don't know that. They just wonder why their turtles died so young. Many times it was just because they didn't have the right amounts of the right kinds of life.
Your turtles should be very happy that you're not one of those people. You're reading this page to learn how to provide your turtle with the care it needs. Good for you!
Luckily, it's pretty easy to give a turtle all the UVB light it needs. In fact, you can satisfy all of your turtle's light needs with one lamp, if you like. There are lamps called "Self-Ballasted Mercury Vapor Lamps" that provide heat, daylight, UVA, and UVB light all in one lamp. They're an excellent choice if you don't have a lot of room or if you want to keep things simple. They've also come down in price quite a bit over the past couple of years. Nowadays they're actually a less-expensive way to light up your turtle's world than using separate lamps.
On the down side, mercury vapor lamps do use a lot more electricity than halogen basking lights and fluorescent UVB lamps. In fact, they use about twice as much electricity as a comparable halogen / fluorescent lamp combination. If you live in an area with high energy costs, that can make a noticeable difference when the electric bill comes in. That's actually why I started using halogen basking lamps. I used to live in the city where the electric rates were high, and my electric bills were getting ridiculous.
Most people choose to use two lamps, usually a UVB lamp of either a tube or compact design, and a separate basking lamp. For aquatic turtles, most experts recommend using a 2.5 percent, 3 percent, or 5 percent UVB lamp. These lamps are often called "Tropical UVB" lamps or "Swamp UVB" lamps, and are the type you should use for aquatic turtles. I suggest that you not use "Desert UVB" or 10 percent UVB lamps for aquatic turtles. Those lamps are made for desert-dwelling reptiles. If you must use a 10.0 temporarily because it's all that's available at pet shops where you live, then move it farther away from the basking platform. It's not a perfect solution, but it's better than nothing.
When using any UVB lamp, it's important to place it at the right distance so that the turtle will get the right amount of UVB light. Usually this is about 12 inches for a UVB 2.5 lamp and about 18 inches for a UVB 5 lamp. The companies that make these lamps usually have excellent information on their Web sites that provide detailed instructions.
Please note that UVB light doesn't penetrate glass or plastic, so don't use a glass or plastic cover on your turtle habitat. Use a metal screen cover instead. You shouldn't use no cover at all because that can be dangerous. Lamps occasionally explode when they get splashed by water, and the glass can injure your turtle.
UVB fluorescent lamps are available in two styles: Tubular (sometimes called Linear), which are straight and come in various lengths for different size fixtures; and Compact (shown on the right), which usually are squiggly-shaped and screw into a regular light socket.
When the compact UVB lamps first came out, there were a lot of problems with them. Some of them didn't generate enough UVB light, and others seemed to generate too much. Some of them also seemed to irritate turtles' eyes. The companies that made these lights went back to the drawing board and re-designed them, and most turtle experts believe that the problems have been fixed. Some, however, still prefer the tubular lamps.
One thing that most experts agree about, however, is that if you choose to use a coil-type UVB lamp, you shouldn't use a mirror-type metal reflector with it. That concentrates the UVB light too much. Use a fixture with a satin metal or white-painted interior, not a mirrored one. If your turtle shows any sign of eye irritation (for example, if it gets puffy eyes, rubs its eyes, or stops basking), then turn off the coil light for a few days and see if it clears up.
Just because UVB lamps are lighting up doesn't mean that they're producing the right amount of UVB light. Usually they have to be replaced at regular intervals even if they still light up. Some lamps say to replace them at six months, and others at a year. What I do if a lamp still lights when it's time to replace it is set the old one aside as a spare in case the replacement fails prematurely. Then I can use the old one temporarily until a new one arrives.
The other kind of light that turtles must have is a basking lamp, which is sometimes called a "daylight lamp." These lights are usually incandescent lamps that screw into an ordinary light socket, and they produce heat as well as light. Some of them have built-in reflectors that focus the beam. Others are round like regular light bulbs or are of unusual sizes that need to be used with special turtle lighting fixtures. There also are halogen basking lights that save electricity.
Basking lights should be aimed at a spot near the center of the turtle's basking area and placed at a distance that heats that spot to the high end of your turtle's temperature range. For most adult aquatic turtles, the temperature at the hottest spot of the basking area should be about 85 - 90 degrees Fahrenheit (or 29.4 - 32.2 degrees Celsius). For babies and turtles who are sick, it should be between 90 and 95 degrees Fahrenheit (32.2 to 35 degrees Celsius).
What you want to do is create a range of basking temperatures so your turtle can choose the one he or she likes. The hottest place -- right where the light is pointed -- should be the high end of the range for your turtle specie. The coolest part of the basking area should be at the low end of the temperature range. By creating a range, you're giving your turtle a way to regulate its body temperature by moving from one spot on the basking area to another. That's why it's important to build or purchase a big enough basking platform. The turtle needs room to move around to find the right temperature.
Don't guess about basking light placement and temperature! Use a reptile terrarium thermometer instead. They are available in the reptile section of pet stores and are not expensive. If you place your basking lamp too far away, your turtle can catch a chill and come down with an RI (respiratory infection), which often is fatal to turtles. If you place it too close, you can burn your turtle. So don't guess about the temperature. Be smart and use a thermometer.
When taking temperatures, take them with the tank cover or screen in its usual position. Tank covers affect how much light and heat get through. When you remove the tank cover (for example, to feed the turtles or work on the habitat), put it back as soon as possible so the basking area doesn't overheat. If you must leave the cover off for more than a few minutes, turn off any heat- or UV-producing lamps or temporarily move them farther away from the basking area. (Remember to put them back where they belong when you replace the cover.)
One convenient way to save both space and money is with a single fixture that performs double duty, like the Zoo Med Aquatic Turtle UVB and Heat Lighting Kit on the right. Other manufacturers make similar products, but I think this one is a good value. I've also had good success with Zoo Med lighting products in general. If I were setting up a new aquatic turtle habitat today and didn't already have a bazillion turtle lamps stored away in my basement, this is the one I'd buy.
Now that I think about it, I actually do use the heat lamp included in this set as a separate basking light on one of my habitats, and the turtles like its light just fine. The halogen lamps are also pretty long-lasting as reptile basking lamps go.
Another thing I like about this combo set is that the basking lamp is halogen and the UV lamp is fluorescent (as are UV turtle lamps in general), so it saves some money on electricity. You'd be surprised how much electricity is necessary to power the heating and lighting in a turtle habitat. Depending on where you live, it can add quite a bit to your electric bill; so saving wattage wherever you can is a good thing as long as you're still providing good light and proper heat for your turtles.
I do have one caution about using combo lamp fixtures: When it's time to replace the lamps, make sure you use the same types of lamps that came with the fixture. The fixture is calibrated in such a way that the UV exposure and the heat produced by the basking lamp are balanced. Using lamps other than those for which the fixture was designed can create an unbalanced lighting condition. Zoo Med sells replacement lamps for the the fixture shown here as a set. Most other well-known manufacturers also sell replacement lamp sets for their fixtures, and using them is your best bet as far as maintaining balanced lighting is concerned.
Another kind of lighting that you'll probably want, especially if you have a big tank, is daytime viewing lights. These lamps are not there for heat, UV, or to keep the plants happy. They're for people to be able to see into the tank.
I personally prefer LED viewing lights because they last pretty much forever and burn very little electricity. I also prefer "daylight" lamps (color temperature between 5000 K and 6500 K, depending on the manufacturer) because "soft white" or "warm white" lamps make the water look brownish and dirty. I've also been told that daylight lamps are better for aquatic plants than "softer" white lamps, but I'm not an expert in that area.
Daytime viewing lamps don't have to be aquarium lamps. I've used LED aquarium lights, BR40 LED flood lamps, and even ordinary A19 LED light bulbs with lamp reflectors like painters use in my aquatic habitats. As long as the color temperature is within 5000 K and 6500 K, it's hard to tell the difference.
If you use daytime viewing lamps, they should turn on and off with the basking and UV lamps to avoid throwing off the turtles' day / night rhythm.
Another kind of light that many people like to use is called a night viewing lamp, or simply a "night light." These usually come in either red or purplish-blue and are designed to allow night viewing without keeping your turtles awake all night and making them grouchy. The turtles don't need them, and most turtles don't care whether they're red or blue as long as they're not too bright. If you have a choice, go for blue. I've noticed that a few turtles seem to be kept awake by red light, but not by blue.
Another kind of night viewing lamp called an infrared heat lamp. They're designed to produce heat as well as (usually) red light. Some provide mainly heat and little or no light. Their purpose is to keep your turtle's basking area warm, which is mainly important for hatchlings, who often sleep on the basking area because their lungs are still very small. Once they get a little bigger and can hold their breath for a long enough time, they start sleeping underwater.
These lamps are also helpful when your turtle is ill because the infrared light helps raise their internal body temperature so they can fight the infection. They basically give the turtle a fever.
If you decide to use an infrared heat light, be really careful with it. Some of them put put out a whole lot of heat and can burn your turtle if you place them too close. They can also burn your turtle if you forget to turn them off when the daytime basking light comes on. The combined heat output of the two lights may be too hot for the turtle. A day / night light timer automates the process so you don't have to worry about it.
Circadian rhythm is just a fancy scientific name for the normal 24-hour cycle that most living things call a day. Like almost all animals, turtles focus their energy on different things at different times during a 24-hour day. This is true on the biochemical level inside their bodies, not just in terms of their behavior.
It's important that a turtle's habitat include days and nights. The natural rising and setting of the sun does this for turtles who live outside in ponds; but for turtles kept indoors in tanks, we have to create their days and nights by turning the lights on and off. In general, the "daytime" lights (that is, the basking and UVB lights) should only be kept on for 10 - 12 hours a day. When the daytime light is not on, either a night light or no light at all should be used.
An aquarium light timer to turn the lights in your turtle habitat on and off is a good investment for your turtle's world. These timers can be purchased at pet shops or at home supply companies and are not very expensive.