Hmmm, interesting observations. I don't use many UV bulbs in my snakeroom, but I will say this: I DO provide, and encourage all keepers to provide their garter and water snakes with at least a full spectrum light, even if it does not give off heat. I have witnessed over and over that this has a dramatic effect on the activity levels as well as the eating habits of my snakes. I generally provide light of some sort to mostly all of my snakes, some tanks directly, and some are indirect. The ones that get the direct light are the snakes that seem to really change their habits if they don't have it, like the blacknecks, the water snakes and the younger garters.