So I researched the UVB flourescent tubes and this is what I found:
I use a Repti-Glo 8.0 24" which starts out at a 55% and drops down to 35% after 105 hours of burning at a distance of 6" from basking area (about 8-10 days at 10-12 hours a day), and gradually declines within a year. Fitted with a reflector, it starts out at 120% and over a period of 1 year, it drops down gradually to about 75%, at 6" away and 10-12 hours burn time per day. Seems a lot less drastic of a decline than the compacts.
Another interesting fact, because I truly didn't understand the UV percentages claimed on the bulbs packaging, this site explains it. A bulb that says 30%UVA and 5-8%UVB ouput has a visible light output of about 62-65%. That means that 5-8% of the bulb's output is emitted as UVB, 30% emitted as UVA and the rest is visible light. It doesn't tell how powerful the tube is, only the proportions of the bulb's output. So, the higher percentage of UVB the package says, the higher the
proportion of UVB, not the actual UVB rays percentage the animal receives.
If the tube bulb is fitted with a reflector (aluminum pre-made or foil home-made), the amount of UVB is almost doubled. Positioning of the light over the basking area is important with the reflector fitted bulb so as not to have the animal be exposed to excessive glare. For turts, most of us postion our lights above the bask area, which keeps the glare in the tank to a minimum.
I apologize if this is too long of a post. I was excited to share the info! All of this is available on the link Grey Goose provided (again thank you!), if anyone wants to read up on it themselves. Also, please correct me if you feel my findings to be inaccurate.
