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UVB Guide v2.0 - What it is, why to provide it, and how to choose the right bulb for your setup!

PinnedTips/Advice

Pacman Frog UVB Guide: What it is, why to provide it, and how to choose the right bulb for your setup!

Written by u/alienbanter for the r/pacmanfrog subreddit and Advancing Amphibian Husbandry group on Facebook (which I now also admin). Feel free to comment or message me with any questions or concerns! Peer reviewed by retired vet and reptile lighting expert Dr. Frances Baines and two additional AAH admins.

In this post, I’ll attempt to explain why providing UVB to our Pacman frogs is a good idea and introduce how to do this safely! As always, if you’d like help with your setup and want personalized suggestions, or just want to check that what you’re planning on using is appropriate, feel free to make a post about it! Just make sure to include as much information as possible (especially the kinds of details in points 1-5 below), and a photo of the enclosure always helps too.

Here is a link to a better-formatted version of this post on Google Drive with page numbers, if that's easier for anyone.

Additional resources:

Table of Contents

  1. What is UVB, and what does it do for animals?
  2. Why provide it to Pacman frogs?
  3. How do I choose a lamp? Target UV index, type of bulb, type of reflector, where the bulb will be mounted, and the distance between the bulb and the frog
  4. An example of these principles in use!

1. What is UVB, and what does it do for animals?

From Dr. Frances Baines’ article An In-Depth Look at UV Light and Its Proper Use With Reptiles:

UVB is invisible to reptiles, but its high-energy short wavelengths are biologically active. The UV in sunlight is an effective disinfectant that can destroy bacteria, fungi and viruses on the surface of the skin. UV also has direct effects upon skin, which include strengthening of skin barrier functions, increasing pigment formation and modulating the skin’s immune responses. It also stimulates production of beta endorphins, giving sunlight its “feel good” factor, and induces nitric oxide production, which has localized protective effects on skin cells.

Figure 1

Perhaps the most well-known and vital effect of UVB, however, is its ability to convert a natural cholesterol in the skin to pre-vitamin D3. Warmth, typically also absorbed while basking, converts the pre-vitamin D3 to vitamin D3. Vitamin D3 is used for vital functions throughout the body (see Figure 1). It is taken up from the skin into the bloodstream, then carried to the liver, where it is converted into a storage form called 25(OH)D3. This then re-enters the bloodstream and is carried throughout the body. A blood test for 25(OH)D3 is the best way of measuring an animal’s vitamin D3 status.

A small amount of 25(OH)D3 is essential for life. It is processed by the kidneys into the active hormone, 1,25(OH)2D3. (Blue arrows on the diagram). This vital endocrine hormone controls the levels of calcium in the bloodstream. Adequate circulating calcium is absolutely essential for muscles and nerves to function, and is also vital for normal growth and reproduction. 1,25(OH)D3 enables the gut to absorb calcium from the diet, and maintains stores of calcium laid down in bone. If a reptile develops metabolic bone disorder (MBD) as a result of vitamin D3 deficiency, this means that levels were desperately low, not even sufficient to make the tiny amounts of active hormone so necessary for life.

However, when supplies of vitamin D3 are plentiful, the liver can produce much more 25(OH)D3 than is needed by the kidneys. (Pink arrows on the diagram). Other organs can take up 25(OH)D3 and turn it into the active form inside their cells. There, it controls as many as 2,000 genes influencing a huge range of functions, including cell division and the immune system. Adequate vitamin D3 is needed for full health, not just the bare minimum that keeps MBD at bay.

In summary, in addition to a variety of other health benefits, UVB lighting allows animals to synthesize vitamin D3 in the skin, which allows them to utilize the calcium we provide in the diet.

2. Why provide it to Pacman frogs?

Pacman frogs aren’t traditionally provided with UVB lighting or overhead heating, and keepers and breeders alike have kept them healthily for decades without these things. Instead, vitamin D3 is typically provided as a supplement in the diet along with calcium, as this vitamin D is what allows them to use the calcium we provide (as explained above). So why do we push for it here?

There aren’t any studies that suggest the amount of dietary D3 to provide, so it’s actually possible to overdose our frogs on it if way too much is provided. In contrast, the natural pathway by which it is produced in the skin under UVB lighting is self-limiting, as explained if you scroll down on this page also produced by Dr. Baines, so as long as you are using trusted lamp brands whose products have good spectral distribution of light wavelengths, D3 cannot be overproduced by the body’s natural processes. (This is not to say that you can’t still provide UVB lighting that is too strong though - that can cause other problems such as photokeratoconjunctivitis.)

This, in addition to the other benefits discussed in the previous section, make quite a good argument for why allowing our frogs to make D3 naturally is best! By providing a gradient in UV light across the tank with maximum levels chosen appropriately for our frogs (as explained below), we allow our frogs to self-regulate their exposure the same way they would in nature as they evolved to do.

This isn’t a completely novel concept in the keeping of nocturnal (or non-diurnal in general) species. Reptiles like snakes and leopard geckos have also traditionally been kept without UVB or overhead heating (heat pads are used instead), but husbandry standards for those species (among some circles at least) have been advancing faster than amphibian husbandry. Keepers of those reptiles who have started to provide UVB and overhead heating have noted increased basking behaviors (including cryptic basking, where only part of the animal’s body is exposed to the light), and anecdotally I’ve personally experienced this with my Pacman frog as well since switching her to a heat lamp and UVB from heating pads.

The science supports this advance as well. Another of the articles linked above, How much UV-B does my reptile need? The UV-Tool, a guide to the selection of UV lighting for reptiles and amphibians in captivity by Baines et al., contains a section on considerations for nocturnal species. I’ve cut some of the section out here for space, so please click the link and go to page 8-9 of the PDF to read more:

It has been speculated that crepuscular species may synthesise vitamin D3 by emerging into sunlight at dusk and dawn. However, when the sun is close to the horizon, the atmosphere filters out almost all the UV-B wavelengths required for vitamin D3 synthesis; species which can benefit from such low levels of UV need skin with very high UV transmission. Some nocturnal geckos, for example, fit into this category. Short wavelength UV-B has been shown to be transmitted through the full thickness of skin of the nocturnal gecko Coleonyx variegatus to a depth of 1.2 to 1.9 mm, in stark comparison with diurnal species such as the desert lizard Uta stansburiana, in which transmission was restricted to between 0.3 and 0.9 mm (Porter 1967). In the same study, Porter found that the skin transmission of seven species of snake reflected their behaviour, such that the highest transmission was seen in the most completely nocturnal species, and the lowest in diurnal species, with crepuscular snakes in between. This suggests one way in which low levels of UV-B may enable adequate vitamin D3 synthesis in nocturnal species. Carman et al. (2000) demonstrated that the skin of the nocturnal house gecko Hemidactylus turcicuscan synthesise vitamin D3 eight times more efficiently than skin from the diurnal desert lizard Sceloporus olivaceous – suggesting that this is an adaptation either to lower levels of available ultraviolet light in its microhabitat, or to very short exposure to higher levels, during brief day-time emergences from shelter.

…

The vitamin D3 requirement of some nocturnal species may be low; passive absorption of dietary calcium by vitamin D-deprived leopard geckos, for example, appears to be effective enough to prevent metabolic bone disease (Allen et al. 1996). However, the paracrine and autocrine functions of vitamin D3 are independent from calcium metabolism; more research is needed to assess the full effects of vitamin D deficiency.

To summarise, some nocturnal animals clearly do have the ability to synthesise vitamin D3 in their skin, and this would occur naturally whenever they were exposed to daylight. So there would seem to be no reason to withhold provision of full spectrum lighting, provided that they are able to spend the daylight hours in an appropriate retreat, with access to a UV-B component suitable for a shade-dwelling or crepuscular species (i.e. Ferguson zone 1).

The argument always comes up with Pacman frogs and other species that they don't need UVB. But what does it mean to need something? If it just means something that's necessary for survival, and our only goal is to provide things required for this, we'd all just keep our frogs in plastic boxes with no enrichment, substrate, lighting, etc. Just water and some food every now and again. And I think most would agree that this would be unethical. By that argument, dogs don't need a yard or toys because they can survive chained in a tiny room - but it doesn't make it right. Because it’s harder to anthropomorphize exotic animals in the same way as domestic pets such as mammals and birds, sometimes people take for granted their ability to survive wide ranges of appropriate conditions, as they do not show much behavioral reaction to them. This is often how bad care guides are produced (comments courtesy of Ricky Johnson). Evidence and anecdote alike demonstrate that UVB is a good thing to provide for our frogs' health, and allowing them the choice of exposure to UVB helps advance our husbandry and give them more freedom.

If this has successfully convinced you to provide UVB for your frog, the next step will be figuring out how to do so safely!

3. How do I choose a lamp?

Unfortunately, providing UVB isn’t as simple as the bulb companies might like you to believe. A number of factors must be taken into account, including:

  • A. The target UV index for the frog
  • B. What type of bulb it is (shape, wattage/length, UVB percentage, version, etc.)
  • C. What type of reflector or fixture it will be used in
  • D. Where it will be mounted (in the tank, above a screen lid, the type of screen, etc.)
  • E. The distance between the bulb and the frog

A. Target UV index

The first step is figuring out how much UV you need to provide based on your frog. Different species are organized into four different categories called Ferguson Zones based on their basking habits in the wild – you can find a big table with lots of species listed in this paper, which also discusses the importance of providing UVB in general.

While they are not listed in the paper, according to Dr. Baines' contributions in the Reptile Lighting group, as nocturnal ground-dwellers all species of Pacman frogs are currently considered Ferguson Zone 1 species. This means that for normally pigmented frogs, providing a maximum UV index of around 1.0 is a good goal, and for albinos, we can cut this in half to provide a maximum UVI of 0.5.

One type of tool that's always useful to have is the pricey but one-of-a-kind UV index meter called the Solarmeter 6.5 or 6.5R. These devices allow you to measure the UV index produced by a lamp and removes any guesswork or assumptions like those discussed in this post. There are a few different places to check for stock! These links will mostly be useful for folks in the United States, but I got mine at Josh's Frogs, and I think they also show up on lightyourreptiles.com, Reptile Basics, and even Amazon (the 6.5 and the 6.5R). The Solarmeter 6.5 currently comes with a few different labels depending on which company is selling them, such as those shown in this image courtesy of Frances Baines.

The next steps all work together to allow you to pick a bulb, but I’ll talk through some of the options for each one.

B. Type of bulb

Generally, there are five main categories of UVB bulbs that are commonly used today in the hobby: coil or compact fluorescent bulbs (CFLs), T8 linear fluorescent bulbs, T5 linear fluorescent bulbs, mercury vapor bulbs, and metal halide bulbs. In this guide, I’ll focus on CFLs, T8s, and T5s, as mercury vapor and metal halide bulbs are generally much too strong to use for Pacman frogs. Depending on your specific setup, a CFL, T8, or T5 might be your preferred choice of bulb, or you might have several options. In a case where any of the options can work, generally speaking, T5 > T8 > CFL.

Linear UVB bulbs are typically deemed better for a few reasons. 1) You can replace the bulbs every 12 months instead of every 6 (or even longer if you have a Solarmeter 6.5 to test output!). 2) For all UVB applications, the UVB needs to cover the whole basking area, which needs to fit the animal in it, and the compact bulbs are too small and produce too small of an area of UVB for many species. 3) The compact bulbs are weaker at distance than most linear bulbs, but they can have a very sharp UVI gradient with very high levels close to the lamp. This makes them often only appropriate for species with low UVB needs in situations where the bulb can be placed so that the animal cannot get too close. So basically, for a compact lamp to be the best choice the animal it's being provided to typically needs to be in a short tank and require low levels of UVB, the animal needs to be small/compact enough for the bulb to work, and the bulb has to be placed so that the animal can’t get too close to it. Pacman frogs fit these categories, so the compact bulbs can work!

If you have a larger and taller setup, a T5 or T8 is likely preferred. T5s are newer technology and come in two versions – T5-HO (high output) and T5-NO (normal output), each of these categories having different UVB percentage, wattage, and length options. T5s typically are stronger, brighter, and slimmer/lower profile than T8s. While T8s are an older style, they can still be quite useful in situations where a softer light or closer approach to the lamp is needed. Both types need to be in reflector fixtures, which are matched for type, length, and wattage and which boost the light and UVB below the tube 2-3x over that of a bare tube (comments courtesy of Frances Baines). For low UVB-requiring species like Pacman frogs, chosen appropriately both T5 and T8 bulbs can work.

Two of the most reputable and highly respected UVB lamp brands are Arcadia and ZooMed’s Reptisun line of products. Arcadia produces T8s, T5-NOs, and T5-HOs, and ZooMed produces T8s and T5-HOs. As an example, one popular lighting choice for Pacman frogs is Arcadia’s ShadeDweller ProT5 kit, which is a 12” long T5-NO bulb. One handy thing about the ProT5 kits is that if you’re setting up a bioactive tank, they can be daisy chained to Arcadia’s Jungle Dawn plant LED lights so you don’t have to use as many outlets.

When choosing what you want to use, you need to take tank length into account. Since Pacman frogs aren’t open sun baskers, we need to make sure that they have plenty of room to escape light in their tanks. For this reason, keep UVB lights to half the tank in length or less. If you have a small tank, this may mean you can’t find a T8 or T5 short enough (for example, the shortest T5 I know of would be something like the Arcadia ShadeDweller, which is 12” long), and a CFL will then be your only option until you upgrade your tank.

C. Type of reflector

The UV output of a lamp can be amplified by the use of a reflector. Arcadia or Vivarium Electronics reflectors can increase the UV output of a lamp by approximately 3x, and the reflector built into ZooMed’s T5 Reptisun Terrarium Hoods increases the UV output by about 2.4x. Other types of reflectors will be less effective, but these are the two most commonly used. Be sure to clean reflectors periodically with a soft cloth (they scratch easily) if you use one to make sure that they stay at optimal effectiveness, as dirt and water stains (etc.) can affect this! If you’re using a CFL, hoods are available to mount the bulbs horizontally, and they can also be used in their vertical orientation in deep dome fixtures.

D. Where the bulb will be mounted

Where to mount the UVB bulb is a choice you will make based on how the position will affect the UV index in the basking area where the frog will be. For Pacman frogs, most people will be placing bulbs on top of the tank above a screen lid. Screens cut down on the amount of UVB that reaches the tank. The mesh that ZooMed and Exo Terra use in their terrariums tends to block about 35% of the light, and Thrive brand “mesh” (more like metal with holes punched in it) sold with their front-opening terrariums blocks more like 65-70% of the light. If you have a Thrive screen lid, replacing it is a safe bet. If you have a different brand, you can post a picture of it in the Reptile Lighting group on Facebook to get help calculating the blocking percentage.

To calculate how much the UVI will be reduced from your screen of choice, multiply the fraction of light allowed through by the known UVI without a screen at a specific distance. Here’s an example: let’s say you have an Arcadia ShadeDweller bulb in the Arcadia ProT5 reflector, and you want to put it over a ZooMed mesh screen. According to this chart from Reptile Lighting, at 30 cm this bulb and reflector produces a UV index of about 1.6. Since the ZooMed mesh blocks about 35% of the light, this means 65% of the light is allowed through. 1.6 * 0.65 = 1.04. This means that at 30 cm under the lamp, using a ZooMed mesh screen, a frog would receive a UV index of about 1.0. This is great for normally pigmented Pacman frogs!

E. The distance between the bulb and the frog

As may have been hinted from the last section, one of the key factors in using UVB appropriately is to keep the bulb at the right distance from the frog to provide the UV index desired. This means that even if you had a really strong bulb, if you elevated it high enough above the tank so that the UV index was still low enough at frog-level, it would still be safe. You can adjust this distance by changing the depth of the substrate, propping the bulb up higher above the frog, or strategically using extra layers of mesh to block more UVB (though doing this last one without a Solarmeter to directly test the new UVI levels wouldn’t be advisable).

Now armed with all of this information, you can look into picking a bulb for your setup! The admin team is working on gathering as many readings and charts as we can find for bulbs that may be appropriate for Pacman frogs depending on the setup, and also some examples of bulbs that won’t work. This partner document will be going up shortly (check back for a link later).

4. An example of these principles in use!

This is my Ceratophrys ornata Atari’s current bioactive setup. It’s still evolving (next step will be replacing the plants with some which are more similar to those found in her native environment of the Argentine Pampas!), but I’m quite happy with the current lighting setup!

Tank front view

The left side of the tank is the warm/bright side, while the right side is cooler and darker. I’m using an Arcadia ShadeDweller for UVB, positioned over a screen lid ~12 inches above the substrate to provide a UVI index of around 1.0, since my frog is not albino. I have this fixture daisy-chained to an Arcadia Jungle Dawn plant LED which is along the back of the lid (see next photo). The larger dome holds a 45W R20 incandescent light bulb, which is used during the day to provide surface temperatures of around 85°F. The smaller dome holds an Arcadia deep heat projector (DHP), which comes on at night during the winter to make an area of warmth around 75°F. The heat lamp and DHP are controlled by a Herpstat 2 dimming thermostat.

Tank top view

Here is a top-down view of the lid showing the placement of the various fixtures.

This document has been approved for posting by Atari :)

Thanks for reading!

Posted Oct 5, 2021, 9:13 PM UTC

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