Wattage has nothing to do with amount of UVB rays produced. You can have a billion watt bulb but it certainly won't produce a billion units of UVB. Two separate things completely and totally unrelated.
The wattage usage is simply how much watts of energy is needed for the bulb to produce maximum light/heat. Typically compact florescent bulbs when saying they are 25 watts but produce as much light as a 50 watt bulb just means it is more efficient, producing more light energy and less heat energy without using up as much power, hence, power bill will be less.
Though I am quite sure the 7.0 UVB compact bulb does produce 7.0 units of UVB, what concerns me is the area of coverage. Only a small area of your tank will be exposed to the maximum UVB the bulb can produce, thus making it harder for your dragon to get full exposure. A long florescent tub puts out UVB along its entire length. The Mercury Vapour bulbs are almost all dome shaped but put out UVB for further distance...even then they don't cover the entire cage (inverted cone area of coverage, so only really hits things directly underneath it but the higher it is the more area it will cover but at a lesser degree depending on how far it is overall (I believe the effective range is something like 24-36" give or take but since MVB's put out something like 50-75 units of UVB, even at 24" the dragon will be exposed to nearly the full strength of the bulb (mmm maybe 45-60 units?). However if you measure at an angle away from the bulb, it may be much less when directly below.
As I don't know how UVB travels from the bulb (globe type radiation, or straight down in a cone, or similar) most of this is guesswork. UVB rays may be very effective at bouncing off objects and eventually fill the entire tank at an 'average' intensity in most areas. Or are mostly absorbed by surfaces and thus little to no 'bounce' or reflection.
Hence, for a large cage (ie 4' long or more) it may be necessary to mount several of the compact bulbs along the top of the cage (facing in of course, or mounted on the underside of the top, inside the tank) to ensure your dragon will have exposure to UVB when not directly under a single compact UVB bulb. The long tubes have the advantage of being able to cover a good portion of the cage with the same intensity of UVB.
Bearded dragons can be overdosed by UVB but pretty much none of the commercial bulbs are anywhere near strong enough to do so. Mercury vapor bulbs mounted to close to the dragon can cause problems, but most seem to be eye problems which may be due to brightness of the bulb, or possibly by the UVB itself. It is also not safe for us to look directly into the bulb while it is on as it can harm the eyes (again not sure if its the actual UVB that is harmful or the brightness of the bulb, i can't remember what was said about this).
However, UVB from the sun, especially during the noon our is many times more powerful than any UVB light in existence (to my knowledge anyway) But, bearded dragons don't tend to lay around in direct sunlight during the hottest and most 'brightest' time of the day, they take shelter in brush, borrows, or other hides. Thus, if your dragon has sufficient hides and can get warm enough quickly under their basking spots, they will move into other areas not so directly exposed to heat and UVB. Not mounting MVB any closer than 18" is also a good precaution.
This is one reason I like to have the highest point of the basking spot around 115-125F thus the dragon can go to the hottest point and move lower down on the basking spot or into the cool end when she is sufficiently warm. Big wide and slowly inclining basking spots are great, not small narrow ones. This gives the dragon more variety of temperatures to bask in and doesn't force them to constantly bask if the temps are just hitting the minimum temps they need. Also the wide basking area allows them to comfortably lounge without worry of falling off the log.
-----
PHLdyPayne
-med.jpg)
