Bearded dragons are diurnal, which means that they are active during the day. And they LOVE the sun. In fact, their parietal (third) eye uses bright light to set the dragon’s circadian rhythm and activity patterns. In other words:
- They must have strong, reliable UVB lighting
- Plenty of bright, white light is needed for energy, appetite, and mental health.
Linear Fluorescent UVB
The Zoo Med ReptiSun 10.0 T5 HO UVB, Arcadia Desert 12%, and Arcadia Dragon 14% are fluorescent bulbs that don’t produce heat, but provide plenty of good quality UVB for bearded dragons in a 24″ tall enclosure. These bulbs are T5 fluorescents, which means that they have a stronger UVB output than standard T8s. They also last longer — up to a year!
For maximum effectiveness and safety, the bulb should be roughly 1/2 the length of your enclosure and placed on the same side as your heat lamps. You will also need to be careful about the distance between the basking area and the UVB bulb, as UVB strength actually varies depending on distance from the bulb, and whether it’s mounted over or under the mesh:
- Zoo Med T5 HO ReptiSun 10.0
- Over mesh: 10-12″
- Under mesh: 14-16″
- Arcadia T5 HO 12%
- Over mesh: 9-12″
- Under mesh: 14-16″
- Arcadia T5 HO 14%
- Over mesh: 10-13″
- Under mesh: 15-20″
*This data is based on measurements taken by Chris Phillips, using the Vivarium Electronics T5 HO fixture.
**ReptiFiles has furnished the above bulb and distance recommendations based on one set of data. It is likely to apply to the Arcadia ProT5 and Tropic Blaze single bulb fixture fairly accurately. However, using other fixtures, such as the Zoo Med Reptisun T5 HO Terrarium Hood, will likely yield significantly different results.
I strongly advise adding 1-3″ to the recommended distance to account for your specific dragon’s height. The basking area should be the highest point in the enclosure, and closest to the UVB bulb.
Make sure that your fixture does not have a piece of glass or plastic to “protect” the bulb. UVB rays are blocked by glass and plastic, rendering that bulb you just spent so much money on completely useless. Naked UVB bulbs are effective UVB bulbs! Don’t believe me? Just read this case from The Reptile Doctor.
UVB Replacement Schedule
- Mercury vapor bulbs — every 6-12 months, depending on manufacturer
- T8 fluorescent — every 6 months
- T5 fluorescent — every 12 months
For more accurate monitoring of your bulb’s UVB output, I recommend investing in a Solarmeter 6.5. This will help you keep track of the UVI (UV index) within your beardie’s enclosure, and whether it is actually getting too much or too little exposure. According to experts, the optimal UVI gradient for a bearded dragon is 0 to 4.0-6.0, from lowest (furthest from the bulb) to highest (basking area). Most normally pigmented bearded dragons can tolerate UVI of up to 7.0 safely, but these levels are not necessary in captivity for optimal health. For a visualization of the optimal gradient, refer to Arcadia’s Lighting Guide for Full Sun Baskers.
NOTE — Certain morphs of bearded dragon with reduced pigmentation (hypomelanistic, albino, translucent) or thin scales (leatherback, silkback) are likely to be more sensitive to high quantities of UVB. They may need a lower-strength UVB bulb, and should be exposed to UVI of no more than 3.0 in the basking area. Bulbs for these morphs should also span only 1/2 of the length of the enclosure, instead of 2/3.
Full-Spectrum Daylight Lighting
Like all reptiles, bearded dragons need heat to digest and maintain their immune systems. Without it, they get sick and die. Since bearded dragons are basking lizards, they use heat most effectively from an overhead heat source that mimics the sun.
Since they are cold-blooded, bearded dragons need a temperature gradient in their enclosure in order to be able to regulate their body temperature. Although they can tolerate very high basking temperatures, they need to be able to escape to cooler areas in the enclosure to prevent overheating. For example, if we were looking at an average enclosure from left to right, the highest temperatures should be at the far left, gradually descending to the lowest temperatures on the far right.
- Basking side surface temperature— 108-113°F (42-45°C)
- Cool side surface temperature — 77-85°F (25-29°C)
- Air temperature gradient — 72-99°F (22-37°C)
- Nighttime — 55-75°F (12-24°C)
The recommended basking surface temperature shown above is based on recommendations in Judish Badham’s 1971 PhD thesis, A comparison of two variants of the bearded dragon, Amphibolurus barbatus (Cuvier) (since then verified by Dr. Jonathan Howard), where rectal temperatures of P. vitticeps were taken when the dragons moved away from the sun, showing that they were done basking for the moment, and presumably having reached optimal temperature. Their findings indicated that the optimum core body temperature of central bearded dragons is 36.3°C (97.3°F), which requires basking site temperatures between 42-45°C (108-113°F) to achieve. Dr. Howard’s basking substrate surface temperature measurements suggest that the basking surface in a bearded dragon enclosure does not need to exceed 50°C (122°F), as this risks overheating the enclosure.
Surfaces like rocks and logs tend to collect heat over the course of the day, becoming significantly warmer than the surrounding air (for example — have you ever burned yourself on a seat belt buckle even though the air in your car wasn’t that hot?). According to a study by Jane Melville and James Schulte, active body temperatures in Central Australian agamid lizards correlate closely with surface temperatures, which means that measuring basking surface temperature is very important (more on how to measure surface temperature later). For these reasons, a stone basking surface should be provided, as this material is best at absorbing heat for bearded dragons to use.
Additionally, most reptiles benefit from a nightly drop in temperature, which science suggests may actually strengthen their immune system (rather than weaken it, as commonly believed). Provided that daytime temperatures are correct, pet bearded dragons can handle nighttime drops as low as 50°F without ill effect. In fact, providing cooler temperatures at night encourages beardies to bask in the morning, which subsequently makes for a more active dragon. However, without adequate daytime warming, these cool temperatures may induce brumation or illness.
How to Heat Your Bearded Dragon Enclosure
Use a high-wattage halogen bulb inside of a dome heat lamp with a ceramic socket to safely achieve the right basking temperatures and thermal gradient. We recommend using a cluster of two Zoo Med Repti Basking Spot or Philips 90w Equivalent PAR38 Halogen Flood bulbs for the most even heating.
For an average 48″ x 24″ x 24″ enclosure, 90w should achieve the temperatures you need. If you need hotter, raise the basking surface (preferably stone rather than plastic, mesh, or fabric) closer to the heat source. If you need it to be a bit cooler (basking surface temperature over 130°F is too high), use a lamp dimmer like the Lutron Credenza plug-in lamp dimmer to reduce heat output.
Having trouble with short-lived bulbs?
- Wash your hands thoroughly with soap before installing the bulb. Skin oils can potentially reduce heat bulb’s lifespan.
- Check your heat lamp. Is it rated for at least 150w? Does it have a ceramic socket? If not, that’s likely your problem, as well a fire hazard.
- Make sure the lamp is plugged into a surge protector. These bulbs are sensitive to fluctuations in electrical supply, making them more likely to burn out prematurely. A surge protector does what the name implies — protects your bulb from surges.
- Ask yourself: Has the lamp taken a fall recently? The filaments in these bulbs are fragile, likely the result of needing to produce UVA. Jostling or falling while the bulb is hot can prematurely break the filament.
- Contact the manufacturer. If you have done everything correctly, it’s likely that you just got a bad bulb. Check the bulb’s warranty, and if it’s still covered, get in touch with the manufacturer to get it replaced free of charge. For example, the Zoo Med Repti Basking Spot has a 3-month warranty!
How do you make sure you’re doing it right?
First, you need to make sure that you’re getting the right surface temperatures. To measure this, you will need an infrared temperature gun. I got an Etekcity Lasergrip 774 off Amazon, and it’s spectacular.
While using your temp gun, make sure that the basking temperatures cover an area at least as large as the dragon’s entire body (including tail), as hot spots can be dangerous. And don’t take temperature readings until the heat source has been going for about 3 hours, as earlier or later will give you an inaccurate reading. Also note that since your dragon’s head and shoulders are a couple inches closer to the heat source than the basking surface itself, the dragon will likely experience slightly higher temperatures than what the temp gun shows.
Second, you need to make sure that your air temperatures are high enough. A warm basking surface is no good if the air is too cold, and too high air temperatures can give your dragon heat stroke. Keep track of the air temperature in the basking area with a probe digital thermometer like the Zoo Med Digital Combo Thermometer and Humidity Gauge, which is inexpensive and I have been quite pleased with in my own use.
You need both a temp gun and digital thermometer to get a complete and accurate picture of your bearded dragon’s thermal gradient. One should not be used without the other!
Every living creature needs water, even the ones that live in arid desert environments. Water is available in three main ways:
Although it’s good practice to keep a shallow water dish in your bearded dragon’s enclosure, bearded dragons get most of their water from their food and from the air that they breathe. Yes, you read that correctly — they can get water from the air. Granted, it’s not very much water. But this small amount of water from ambient humidity helps keep their lungs, skin, and scales healthy.
A common misconception about bearded dragon husbandry is that humidity should be as low as possible, and any instances of relatively high humidity put the dragon in immediate danger of illness. People who perpetuate this myth forget that Central Australia is not bone dry, and it does rain, and humidity does rise occasionally. It’s also important to note that the average human home significantly drier than outdoors, and sometimes too dry, especially if you live in an area with a naturally dry climate. (Fun fact: the ideal indoor humidity for humans is 40-45%.)
The ambient humidity in your bearded dragon’s enclosure should average between 30-60%. You can measure this using the abovementioned Zoo Med Digital Combo Thermometer and Humidity Gauge, with the humidity probe placed on the cool end of the enclosure. Lower or higher than that, and your beardie may start to develop respiratory problems. It may also cause problems with the skin and scales, especially if the substrate is frequently wet. However, occasional brief spikes in humidity due to watering plants in the enclosure, rainy weather, or nighttime is perfectly natural and safe.
Heat and humidity have an inverse relationship. Where it’s hot (such as your basking area), humidity will be low — potentially as low as 10%. Where it’s cool, humidity will be higher. This gradient of temperatures and humidity, as long as they are within correct parameters, will be beneficial, not harmful.