There are many things being discovered and still plenty of things about bearded dragon care we still don't know.

Naturally a bearded dragon's body will stop producing D3 once it reaches what it needs each day..even if they are still exposed to UVB rays. What they can't do, is stop their body from absorbing D3 taking in via diet (ie supplements) hence the worry of D3 toxicity by over supplementing.

What, to my knowledge anyway, we don't know, is exactly how much. D3 a dragon needs per day to facilitate all the natural body functions per day. For all we know, bearded dragons only need a total of 1 hour exposed to typical UVB levels experienced at sunrise. (which I think is something like 50 units but I could be off, don't have time to hunt down the actual value).

There is also the three or four part process of calcium usage in bearded dragons and most other day active reptiles. Exposure to UVB which is needed to create Vitamin D3 which in turn is required to make use of ingested calcium.

The calcium ingested by the dragon must also be accessible (ie not bonded up by oxates, phosphorus and other calcium binding elements (which is why spinach and kale are not the best despite having fairly high levels of calcium). So making sure the calcium eaten is usable is a sort of forth part.

If any of these parts are missing or insufficient then it affects the entire process. So you need a good source of UVB, a good source of D3, good sources of calcium etc to make it all work. I really don't think its possible to have too much UVB exposure..depending on the UVB index. High UVB index is damaging even with short exposures, but low levels of UVB index exposure is fine with little or no risks. Prolonged exposure of high UVB Index can cause things like skin cancer in us humans...and other conditions in reptiles such as photo-kerato-conjunctivitis.

High basking temps are beneficial as they are needed for reptile bodies to properly produce Vitamin D3, so an appropriately heated basking spot is necessary with access to more than just a single basking temperature in the necessary range. As UVB exposure should include most of the tank, not just the basking area, I don't feel having a higher basking temperature available at the highest point of the basking area is detrimental to total amount of UVB exposure. The idea being the basking spot should have multiple layers, not just one or two. The top most level I feel should have a higher than normal basking temp (say 130-140F), the next level down should be more 110-120F with the third level falling 100-110F and either the floor beside the basking area being 90-100F. This allows the dragon to choose how hot to bask in. This should be adjusted to fit your dragon. If he is always on the floor or in the 100F zone and never seems to use the hotter part, then lowering the wattage of the bulb can be done..to ensure more use of the basking area. In the past I have seen my dragon using the hottest part of the basking area first thing in the morning and right after eating. Once she reached her preferred temperature or exposure, she moved to lower areas of the basking area, or romp about the cage. Mid day she often went into her hide or under the basking area. But came out late afternoon early evening to bask, romp about more till about an hour or so before lights out. Though sometime she just stayed on her basking spot and slept there.

Each year we learn more about reptile care, new better products come out each year as well. Some prove bad (as are some of the compact florescent bulbs but many have been reformulated since manufacturers realized the problems), others very beneficial. As more research is done in reptile care, and the demand for better products increased as reptile pets become less and less of a tiny niche market compared to other pets, improvements will continue. I like to learn each new method and read all opinions, digest what is said pro and con wise, apply logic to it, research points I am not sure of, ask questions and see what makes the most sense.

Many methods work very well with decades of success. It doesn't necessarily mean new or little known methods that are also working for individuals are wrong...just different. Some are bad, yes, especially the more adaptive species who tolerate user errors far better than others.

There was a time mice were kept in cages with cedar chips and they seemed to thrive quite well. But they only lived 2-3 years. Everybody felt that was the natural life span for a typical domesticated mouse. Then research revealed the oils in cedar chips acted as a toxin to mice. Not enough to kill them out right but it greatly stressed their livers and shortened their lifespan. When mice were housed on aspen shavings it was found they lived much longer 3-4 years on average. Maybe a year longer of life isn't a huge difference, but this is a prime example that even the old 'true and tried' methods are not necessarily the best method once new research found the flaws.

Also, keep in mind that many long term breeders/keepers of reptiles had to wing it from 'scratch' and found what worked for them. But many had little to no contact with others of their ilk...except at the few and far between reptile shows etc. where they can exchange ideas. The World Wide Web made it immensely more easy for reptile owners to discuss different methods. In some ways I think over the last ten years, the rapid increase of knowledge over the internet has made many keepers, both new and old, 'lazy'. We go for the simple and ease of cleaning..instead of the more 'zoo' method of recreating the natural habitat as closely as humanly possible. That and we want to cram as many cool reptiles in the smallest space possible while ensuring the reptile's basic needs and ensure easy care and maintenance on our part.

This gives ups the 'bare essentials' method, and 'everything they need and make it nice too' method which is more advanced both in setting up and daily maintenance. Then the middle ground which combines the two extremes.

Bare essentials for bearded dragons would be:

40-50gal breeder tank (single adult dragon)
basking log
hide
water dish
UVB bulb
Basking light providing surface temp of 95-115F, air temp low 90sF basking end, 75-80F cool end
Paper towel (or newspring, reptile carpet) substrate.
Thermometer with probe.

Zoo level would be:

5'x2'x2' enclosure (or larger if multiple dragons)
soil/sand mix substrate, 6" deep, gravel layer for drainage with top inch nearly bone dry with subsequent layers having more water content. Possible bioactive as well.

Natural hides and basking areas of rock outcroppings, logs, etc.
Basking spots providing a high top temperature of 130-140F with lower basking temps decreasing the lower down the basking area one goes.

Live or fake sturdy dragon safe plants arranged to be pleasing and provide shady areas.

High UVB producing bulb such as Mercury Vapor Bulbs or halogen UVB bulbs. Or exposure to natural unfiltered sunlight due to outdoor enclosure or skilight/windows that are non polarized (won't block UVB. All standard window glass is polarized to block about 98% UVB)

etc.

A middle ground will combine elements from both extremes.
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PHLdyPayne

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