Most UVB bulbs are worthless IMHO. Some of the newer ones, the Powersun Bulbs I think, are actually the equivalent to midday sun in some parts of the world. Most of my stuff is nocturnal so I don't worry about it, but my Iguana and Tortoise spend their summers outside in the natural sun, and are supplemented during the winter months. A good cal/d3 supplement is important, but the liquid d3 supplements (ie- solar drops) have an increased risk of causing d3 poisoning to the animal. If your animal is receiving natural UV rays, or is eating a diet consisting mainly of whole prey items (ie- a monitor fed mainly rats) then you can hold off on additional d3 supplementation. But to answer your question, yes the d3 supplements do work, but some animals cannot process them as well, some do not need them, and some can be raised completely on them. It all depends.
Originally posted by Gary D.
Myself, I'll stick with the tried and true flourescent tubes.
Those tried and true fluorescent bulbs still put out very low output, and are almsot ineffective when placed on a screen or if they animal is more than a foot or so away. I think it is something like 24 hours of up close, unobstructed exposure is the equivalent to 5 minutes of natural exposure