Here is what the resident expert told me in the UV member group discussion I talk to just recently when complaining about the reptisun bulbs:
Hi, Wayne.
The ZooMed Reptisun 10.0 linear tubes test results are very good indeed (in respect of spectrum, total output, quality of build and longevity) for fluorescent tubes, and I'm not aware of an equivalent brand available in the USA.
The sample 24" T8 (1" diameter) lamp I tested last year reached 4,000 hours (1 year) of use in one of my vivaria, a few months ago.
It started off at 30 uW/cm2 (UV Index 0.9) at 12 inches distance. after burning-in for just over 100hrs, it gave me 24 uW/cm2 (UV Index 0.7).
Then after 4,000 hours, the reading at 12" was still 21 uW/cm2 (UV Index 0.6) which is extremely good indeed, a very low decay rate.
What distances were your 6.2 Solarmeter from the tube, where you got the readings of 10 - 15 uW/cm2?
I was getting 13uW/cm2 (UVI 0.4) at 18" after burning-in.
You're right, outdoor sunlight when the sun is high in the sky has far more UVB than any safe UVB-emitting fluorescent tube mounted at a sensible distance above a reptile.
However, the readings from a Solarmeter 6.2 from a lamp cannot be compared directly with readings from sunlight, because the spectra of these two light sources are very different.
The Reptisun 10.0 spectrum has a greater percentage of its UVB in the shorter wavelengths than does sunlight.
According to my meter readings, 31 - 32uW/cm2 from a Reptisun 10.0 lamp is equivalent to approximately 40 - 50uW/cm2 of sunlight.
With fluorescent tubes, the general concept is to create a wide zone of "background" UV, rather like daylight "in the shade", so it's okay, you're not aiming to match the intensity of full sunlight in the basking zone. (If you want that, the only realistic options are mercury vapor or metal halide lamps.)
With a fluorescent tube, fitted with an aluminum reflector, you are aiming for maybe UV Index 2 - 2.5 across a large area including the basking zone, for a morning-sun-basker like a bearded dragon.
A ReptiSun 10 tube fitted with a reflector will likely give you that at about 8 - 10 inches above the dragon's back. (You're looking for a Solarmeter 6.2 reading of around 60 - 80 uW/cm2 to get UVI 2 - 2.5)
But if you can fix up an outdoor pen for your beardies, with shade and sun, your Florida sunlight would be much better than any indoor alternatives, when the weather permits...
Best wishes,
Frances
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