Help with solar meter 6.2 for a newbie

[KendraA]

What is the ideal UV Index range for a bearded dragon's enclosure?

I'm reading conflicting things.

On the one hand, the "shade method" indicates that a UV Index over most of viv of 1.5 to 2.0 (a solar meter 6.2 reading of 49--65.5) is just fine.

On the other hand, Arcadia publishes this guideline, http://www.arcadia-reptile.com/wp-content/uploads/2012/04/guide-bearded-dragon.jpg which would indicate that the basking basking zone needs a UV Index 4.8--6.10 (a solar meter 6.2 reading of 160--200), while the rest of the tank needs a UV Index of 2.10--2.75 (a solar meter 6.2 reading of 70-90).

These are pretty different, and I'm not sure which to follow.

 

[KendraA]

I read about the "shade method" a ways down in this forum, in a post by Frances of uvguide.co.uk:
viewtopic.php?f=34&t=121986&p=1158024

 

[Taterbug]

I ended up getting the 6.5 (UVI)- the usage seemed much simpler to me and I like that it can be used for comparing brands and even sunlight.

The shade vs patch of sun - you want to provide either low levels of UVB over a
long time, or high levels for a shorter time to provide a "dose". The idea is that either method will synthesize the needed D3 over the course of a day. The Arcadia philosophy is that basking reptiles are "solar powered" and we should emulate their basking preferences when we can. I get the impression the patch of sun idea is considering other aspects of reptile behavior/response than just what's needed for d3 production.

My interpretation then is that sun-loving reptiles may do better in an environment were they can behave and be exposed to UVB as their instincts would drive them to do - bask out in the hot sun with high UVB, and to retreat to the cool shade with low UVB.

The limiting factor is often the bulbs. The T8 fluorescent bulbs don't produce enough UVB for the patch of sun technique. MVB and the newer T5HO produce more intense UVB and are better suited to it. The T8 basically necessitates the shade method. Of course, cage size will often dictate what you can realistically do as well. A smaller cage cannot have much gradient - thermal or photo.


I think you had another post asking about uvi vs irradiance... my understanding is...

uW/cm^2 is power per unit area. The 6.2 is measuring the actual total irradiance coming from the light source, over the sensitive range (which reaches into UVA and UVC). Since bulbs all have different spectra and the peaks and valleys are so different the number can be the same even if the spectra produced are very different.

UVI is a unitless number that describes intensity relative to the response of human skin to UV radiation. So the UVI meters basically measure the radiations' ability to cause sunburn (or D3 production - since they are similar frequencies). Ideally both meters and the 5.7 could be used to really understand the output - but that's 500-700$ worth of meters....

I hope that helps?

 

[KendraA]

Yes, that's super helpful, thanks a ton! I'm starting to understand these nuances better... and I think I'm going to go with a 22" T5 bulb in my 36" tank, either the Arcadia 6% or 12%, or the Reptisun T5 HO 5.0 or 10.0. And just make sure I provide lots of protected spots.

 

[Taterbug]

It's tricky especially when it seems like the best we can do is "make due" with what's available.

I upgraded recently to the t5 reptisun 10, and was torn too. I haven't installed it yet but I hope the 10.0 isn't too strong. Arcadia sound like great products and I like the company from what I can tell - but the bulbs were double the price. If you have amazon prime the reptisun price can't be beat.

 

[KendraA]

I was thinking, if I go with the Reptisun T5 HO 10.0, that I could mount it in the Zoomed hood and just leave it on top of the screen to cut a little of the UVB. If I got the T5 5.0, though, I thought I might want to put it under the screen. I keep reading conflicting things on whether the Reptisun T5 5.0 is strong enough; meanwhile, I also read conflicting things about whether the T5 10.0 is too strong, so, I know what you mean!

 

[Taterbug]

If you are getting the zoomed hood some vendors ship it with a 5.0 for the same price. Since that fixture has a reflector the output of the 5.0 sounds like it will be similar to what a T8 10.0 is. I guess if it's too weak you replace it with a 10.0, but if not it's all set? You can also use distance (raise/lower the hood) to adjust intensity as well.

I went with the 10.0 since I didn't get the zoomed hood and the fixture I got doesn't have a reflector. I plan to mount it inside in the front corner of my cage - I'll be able to maintain the most adjustable distance there and if I need to I'll add a reflector. At least having the meter will help take the guess work out of knowing of the setup is adequate.

Have you joined the UVB meter owners group on yahoo? They may have the information in their "files" and you could use that to help pick.

 

[KendraA]

I hadn't thought about the reflector making a big difference, but that makes a lot of sense, so maybe I'll try that setup first. I'll definitely check out that group too, thank you!