Corn snakes do not require UVA/UVB lighting, it can be harmful to them . . . I use a heat light on some of my vivs
I have probably said it before, but I will say it again (and by no means am I singling you out Susang--I'm just speaking more in general). There is no conclusive evidence, let alone really any at all, at this time that I am aware of, that the use of UVA/UVB lighting on corn snakes is harmful. This seems to be a common misconception, that someone said on a forum at one time or another, which is now being reverberated by a great number of people. Allow me to explain further.
If you go into a petstore, especially one of large chains, and some of the times the mom-and-pop shops, they probably will tell you that corn snakes need UVA/UVB lighting. Why you ask--well because they live in the same world we all live in (at least if you reading this), which operates by the almighty Dollar (Loonie, Euro, Shekel, etc.). They are trying to make a buck and will sell you just about anything. Now don't get me wrong, usually if a petstore tells you something, you will want to go in the exact opposite direction. But in reality, there is nothing wrong with providing your corn snake with a UVA/UVB light.
In fact, unless you are running a HID or Metal Halide, because you shut down your saltwater aquarium because it was just too much of a pain or it sucked every last dollar out of you (leaving no money left for more herps--which is always a bad thing), then more than likely you using a florescent, which produce much less ultraviolet light than the sun. At this point, you probably like so what danvega, you haven't really said anything--well let me explain.
No corn snakes may not need UVA/UVB light--the fact is we really don't know. I keep on asking my guys and girls, but they always just respond with, "mice again, why don't we ever go out for Chinese anymore?" Seriously though, here's a breakdown: UVA is the visible light, while UVB is the non-visible light.
To start with the latter, it is well documented than many types of reptiles need UVB light because it helps them manufacture Vitamin D3, which is extremely important for proper bone development and avoiding metabolic bone disease among other ailments. However, this is primarily for many of our herbivorous friends. So unless your corn snake is strictly on a diet of salad, it will obtain its D3 from its meaty prey (there are some snakes that do require UVB light though). So UVB light is not known to be needed. However, animals have an uncanny way of surviving (i.e survival of the fittest right). Some folks have theorized that snakes will adjust there living and may be able to maximize D3 through UVB light. This theory is neither proven/disproven. So what about the harmful effects you ask. Well, UVB is the cause of sunburn in humans. But, the composition of mammalian skin and snake skin is somewhat different. There have been tests showing that snake skin from albino and lighter skinned snakes lets through more UVB light. But this necessary does not equate to being harmful--snake skin is still thick and sheds quite often. There have been cases of snakes under UVB lights forming cataracts and other eye problems, but these cases are sporadic at best and there is no conclusive evidence, nor plausible link between UVB and cataracts (too many other factors).
As for UVA, the visible light, corn snakes may actually benefit from having it, as long as it is not left on 24/7. The visible light may help them with their daily time schedule and if used in proportion to the seasons, then it may also help them with their yearly schedule. I do place some weight on this theory, but for the most part, UVA enhances our viewing experience--so we can see them better--and if can't enjoy your snakes, whether in their vivs or out, then why even have them.
I think the key is that everyone must make the decision as to what is best for the snakes that they care for. Me personally, I only use a UVA/UVB light on one of my snakes--my amazon tree boa. And, its really not for it personally, rather for the plants in his vivarium. The rest of my group--corns and balls--live in tubs and it would be impossible and impractical to have lights for each. I do, however, open the shades to brighten the room. And its weird because some of them will come out everyday and lay out on the side of the tub by the windows, while others will never come out during the day.
It's important, whether you chose to use UVA/UVB lights, natural sunlight, or no light, is to provide them with enough cover so if they want to hide to avoid the light, they can. However, I strongly discourage the use of heat lamps. Even if regulated, they will ultimately dry out the environment (unless you religiously mist) and pose too many risks, in my opinion (fire hazard potential and for burns--even outside of the viv), which outweigh any benefit. If we were talking about beardies, then a heat lamp is almost essential, because they love to bask. However, corns generally do not bask from overhead heat (unless that is all that is available to them). They may lay where the heat lamp is, but more than likely they are enjoying the heat from where the lamp heated up the surface--this is why some of the best herping occurs after the sun goes down when they all come out to get the heat from the roads (also makes for a lot of runover snakes).
So to recap, if you have made it this far: UVA/UVB is probably not necessary, but at the same time it probably is not harmful. Either way, everyone needs to make the best decision for their respective animals and provide them with the best care that each of us can respectively do. Finally, if anyone knows of a scientific study (i.e. peer reviewed journal article) providing that UVA/UVB is harmful to [corn] snakes, let me know.
