I definetly make enough money in a week to be able to afford 5.0 bulbs for all of my animals year round...but I refuse to buy a product that is no more beneficial than placing my chameleon in front of a glass window for a few hours a day.
HERE ARE THE FACTS:
Glass filters up to 95% of UVB and UVA rays, while screen filters up to 60% of UVB and UVA rays. The bulbs you are so fond of contibute 5.0% (or less after they deteriorate) of their light to UVB rays. The other 95% is just plain old everyday light.
UVB is a group of wavelenghts that in many reptiles and other animals (birds, and certain mammals) reacts to create Vitamin D3. Vitamin D3 is essential for reptiles to be able to retain their calcium levels. Hence, if I am providing the proper levels of D3 they will be able to retain these calcium levels.
You may be asking yourself: Why doesn't everyone just use Vitamin D3 then if it's that easy???
Well, since Vitamin D3 can be very toxic in high doses...I wouldn't say it's a good idea to use it if you are the average reptile keeper. Actually D3 would be the main ingerdient in most rat poisons.
There is no doubt that UVB bulbs are the safest and best way to ensure your reptile is getting the radiation it needs...but it's too bad the bulbs are not perfected to the extent that they must be replaced every 3-6 months (in my opinion) and they are unreasonably priced. The bulbs deteriorate so fast and like I said before: "If you have a screened enclosure, and you place a 5.0 bulb on top...only 2.5% is now going to make it through...
IT IS A FACT: That these bulbs only work at their maximum percentage when they are placed 12-18 inches from the animal. Since we do not enjoy keeping our chameleons in shoe boxes we decide to give the very large homes>>>4x2x2's or 6x4x2's.
In these types of large enclosures the bulbs are nothing more than useless. The chameleons can barely get high enough to cover the 12-18" they need to use the bulb and we refuse to put the bulb in the tank because of the fact that veiled's and other chameleons are heavy, and excellent climbers. There is no doubt in my ming that a chameleon would not try to climb up on the bulb...burn itself or dislodge the bulb and have it brake...or something of the sort.
Some people lately swear by these NEW MERCURY VAPOR BULBS...in my opinion they are equally useless to the previous bulbs mention except far more dangerous. If the bulb gets wet it could explode causing a leakage of mercury...which is toxic to humans as well as your chameleon...the bulbs also produce far too much UV to be safe and should never be used as a primary heat source...
One areticle I have read was about a dead bearded dragon autopsy...they found mercury in the blood tissues of the dragon due to the POWERSUN vapor bulbs.
In the winter due to cold weather...our chameleons will continued to be supplemented with Vitamin D3 until a problem occurs. Since we've been doing it for more than a year and a half...no problems in temperment or health have occured. Currently their crickets are dusted with a Vitamin/Calcium mixture which contains 22,000 IU/kg...this mixture has caused us no problems and was developed by a local breeder who has kept and bred chameleons for over twenty years.
In his early days there were no UV bulbs so all he had was natural sunlight and supplements. May I mention he also has his Masters in Herpetology?
I myself am currently finishing my 4th year of univeristy Biology and next year I will start my first Herpetology course.
I definetly DO NOT consider myself an expert...I am simply a 4th year univerity student who enjoys keeping and breeding reptiles as a hobby and selling them to make a small profit. I read many books and articles on the species I keep and I come here to recieve other peoples opinions.
Your opinion is obviously that UV bulbs are the best thing since sliced bread...my opinion is slightly different.
I am only looking for an answer to how much of a dosage others are using who supplement with D3.
If I sound uneducated, or offensive at times it is only because I don't like to take the time to explain myself to the full extent...which is what I have tried to do with this post...usually I keep thing short, to the point...things are easier that way.
If anyone has any comments or suggestions with supplementation, how I keep my chameleons or anything elss...feel free to post another message or e-mail me...
Here are our chameleon cages that have just been built...I'm also no expert with construction...but they work...the only change that has been made with these cages...is recently we placed a 48" light fixture and put in two 48" bright light flouescents.

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Chris Vanderwees
REPTILE SALES AND INFORMATION
E-mail Me
1.2.0 Bearded Dragons
1.2.0 Green Basilisks
1.1.0 Crested Geckos
1.2.0 Veiled Chameleons
1.1.0 Corn Snakes
1.0.0 Tokay Geckos
0.0.1 California Kingsnakes
2.5.1 Leopard Geckos