Red Eared Slider Lighting Requirements

Like most reptiles, when it comes to lighting red eared slider have very particular needs. In the wild, they benefit from the presence of three elements of light that are provided by natural sunlight: UVA Rays (Ultraviolet A), UVB Rays (Ultraviolet B), and heat. Each one of these plays a role in your turtle’s development, metabolism, and growth. This is why when you are figuring out your red eared slider tank setup, you should provide a light source that has all three elements so that your red eared slider’s healthy lighting requirements are fully met.


Three Elements of Light

UVA Rays

  • Essential for stimulating activity such as feeding and mating
  • Most common light sources emit UVA

UVB Rays

  • Necessary for the production of Vitamin D3 that is required to metabolize dietary calcium
  • Many turtles in captivity suffer from calcium deficiency because of inadequate UVB ray exposure
    • This is because most common light sources filter out UVB rays (they cannot pass through glass)


  • Encourages your turtle to bask, allowing them to raise their body temperature
    • Basking also strengthens the shell and reduces algae growth
  • Fuels proper function of metabolism, digestive system, and immune system


Light Source Options

NOTE: Never look directly at a turtle light. They are extremely bright and can damage your eyes.

Fluorescent Bulb/Basking Light Combo

Fluorescent bulbs are the most commonly used type of lighting by turtle keepers. These bulbs provide UVA and are specially manufactured to allow UVB rays to pass through the glass as well. When paired with a basking light (provides heat), these combination lights satisfy your red eared slider’s heat and lighting requirements.

Also note that fluorescent bulbs need to be replaced about every 6 to 10 months. The UVB-providing protion of the light bulb has a shorter lifespan and will fail before other elements of the bulb. UVB is not in the visible spectrum of light, and a bulb that is no longer putting out UVB will still produce light; keep this in mind and replace your bulbs at regular intervals. A last note about fluorescent bulbs is that they should not be placed too far above your turtle’s basking area, as UVB rays are pretty short range. Depending on your UVB output %, check the recommendation on the packaging and follow their suggested suspension height.


Mercury Vapor Lamps

Self-ballasted mercury vapor bulbs, also known as UVB heat lamps, are you one stop shop for your turtle’s lighting needs. They provide UVA, UVB, and heat all in one package while lasting longer than fluorescent bulbs. Their main downside is that they are power guzzlers, and can use up to twice as much electricity as a fluorescent/basking light combination. However, once you factor in the convenience of having one fixture to meet all your needs it makes for a great choice.

These bulbs have considerable strength, and extra care should be taken when determining how far above your basking area to place them. Carefully follow the instructions provided by the mnufacturer.



Placing your turtle’s tank in a part of the house with a lot of natural sunlight could seems like a tempting solution to the UV ray problem, but unfortunately it’s not so simple. UVB rays are filtered out by glass and plastic, and even UVB producing light bulbs are made with special glass casings that allow the rays to pass through.

If you live in a warmer area it is possible to bring your turtle outside for a bit. Outside, its UVB ray requirements can be met with about 5 hours a week of natural sunbathing. Be warned, though, that having your turtle outside makes it susceptible to predation by other animals, and if there is not enough shade and your turtle overheats this can be fatal.

Lighting Set Up and Temperature

Once you’ve chosen your lighting, the next step is to make effective use of it. The lighting is meant to be focused on your turtle’s basking area, and you want to make sure you have the temperature range correct. This can mean raising and lowering the light until the basking area registers the correct temperature range. Your best tool for this is a reptile terrarium thermometer, which will cut out the guesswork.

You want to make sure that your red eared slider’s basking area is heated to about 82-88F (27.7-31C). Make sure to check with your thermometer that the temperatures are not higher or lower than this range. Temperatures too high can burn your turtle, and temperatures too low can lead to problems like respiratory infection.

Keep your light fixture aimed at the center of the basking area. This allows your sliders to move closer or further from it depending on their temperature preference.

For more info on basking areas, see our basking area post.

Circadian Rhythm

As a last note, when setting up your turtle tank it is a good idea to give some thought to your turtle’s circadian rhythm. The circadian rhythm is the 24 hour biological clock that animals (including humans) rely on to regulate their metabolisms. To maintain a healthy rhythm, make sure that your slider’s tank lights are only on for 10-12 hours a day so that they have adequately long nights. If you want to automate this function, aquarium light timers are available that allow you to pre-set your “sunrise” and “sunset”.


Keep Reading: Red Eared Slider Care Sheet

  1. Tank Size and Setup
  2. Filter and Water Temperature
  3. Lighting/Heat Requirements – Current Page
  4. The Nitrogen Cycle
  5. Tank Cleaning and Water Chemistry
  6. Diet and Nutrition
  7. Illnesses and Injury
  8. Additional Reading and Resources