Natural UVB from the sunis the best source of d3 for herps, howevevr it is not necessary in captivity if given the correct supplementation. UV bulbs pale in comparison to the suns rays, and IMHO aren't even worth it. If they were good enough you wouldn't need to be supplementing your animals with a d3 supplement in addition to lighting. It is a highly debatable topic, and I know I am gonna get a whole lot of static off this post, but hey... can't fight the facts, right? The Iguana zoo over in Europe has been breeding, producing, and raising iguanas for many generations, as well as many species of varanid and other diurnal lizards without any UV lighting, and many of the monitor breeders in the states do as well. Animals will not breed, let alone produce healthy animals, unless they are being kept in optimal health and conditions are prime.
Those drops you see can and will do the trick, but with liquid d3 supplements you have to be careful. They have a decent concenrt
tion to them, as well as I have heard stories of resulting overdoses by them. Not gimmick for newbies, though most products you find in stores are, just a supplement