Red-Eared Slider UVB & Lighting Requirements

red-eared slider uvb lighting

Each species of reptile has gradually evolved over the course of millions of years to be very good at living in a very particular environment. As such, a reptile’s health and wellbeing is heavily dependent on the environment that it is living in. They’re not as adaptable as mammals like humans and dogs and cats. So when you bring home a pet red-eared slider, you need to make sure that its enclosure replicates the natural conditions of its native habitat. Once a suitable enclosure has been selected, the habitat replication process starts with mimicking the effects of the Sun.

Sunlight is complex, but if we simplify it, we can divide it into the 3 general components that are most important for successful reptile husbandry: infrared (heat), visible light, and ultraviolet radiation.

Let’s start with ultraviolet radiation, or simply ultraviolet (UV). Many people freak out about ultraviolet because when they hear “radiation,” they think about nuclear fallout and catastrophic meltdowns at nuclear power plants. But there are many different types of radiation, and while some are harmful, others can be beneficial.

Ultraviolet-B, or UVB, is a type of ultraviolet radiation that is essential to reptile health in both the wild and in captivity. One of its most well-known function is enabling the synthesis of vitamin D within a reptile’s body. But it also has many other benefits, including strengthening a reptile’s immune system and stimulating the production of the feel-good hormone serotonin.

A good red-eared slider setup MUST include access to UVB (Acierno et al., 2006). So in order to meet this requirement in captivity, you will need a strong, high quality UVB lamp, mounted at a safe distance from the basking area.

Red-eared sliders are classified under Ferguson Zone 3, according to The UV Tool publication by Dr. Frances Baines et al. If you have a Solarmeter 6.5 (recommended), the UVI on the basking surface should be between 3.0-4.0. UVI should be highest at the basking spot and lower in other areas of the enclosure so your turtle has options to choose from.

If you don’t have a Solarmeter, here’s a fair guide to distancing with each bulb type. The given distances are the distance between the lamp and the turtle’s back while standing on the surface closest to the UVB lamp:

ReptiFiles does not recommend placing UVB lamps closer than 10″ to the basking area, as this does not allow the UVB rays to spread far enough to cover your turtle evenly, particularly in the case of large adult individuals.

Your red-eared slider’s UVB bulb should be 50-75% of the enclosure’s length, mounted over the basking area (overlapping with the water area isn’t bad thing, though). Use a fixture with a reflector so you don’t accidentally waste any of the UVB — the above measurements are compatible with the Arcadia ProT5 and Vivarium Electronics fixtures.

The above estimations assume that there is no mesh between the turtle and the UVB lamp. If there is some kind of screen or grid present, see the Facebook group Reptile Lighting > Guides > Guide 1: Using T5-HO lamps above a Mesh Screen for recommendations on adjusting basking distance appropriately.

What other lights do red-eared sliders need?

Although UVB lamps and heat lamps (we’ll get to that later) do produce some visible light, they simply don’t produce enough of it to get anywhere close to replicating daytime illumination. It is highly recommended to also add a 6400K or similar full-spectrum fluorescent or LED lamp to further illuminate your enclosure. Aside from making for some great photos, this extra light can help improve your turtle’s mental health, and is essential for growing healthy live plants in an enclosure.

Here are some of ReptiFiles’ favorite “daylight” lamps:

DO NOT use colored lights of any kind with your red-eared slider’s enclosure (red, black, blue, etc.), not even during the night. These can negatively affect your turtle’s mental health since their eyes are so sensitive to color in their environment (source). And honestly, it looks weird and unnatural.

How long should you leave the lights on?

Red-eared slider lights should be kept on for 11-13 hours/day, with a shorter “day” period during winter and longer during summer. Using digital or smart light timers like the Kasa Smart Plug for this is VERY helpful.


  • Red-eared sliders need high-quality UVB lighting to thrive.
  • Zoo Med and Arcadia are the most reliable reptile UVB brands in the USA.
  • Use a linear fluorescent UVB bulb 50-75% of the enclosure’s length.
  • Distance between the UVB lamp and the basking surface matters.
  • Additional daylight lighting is highly recommended.
  • Lights should be turned off at night.

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