This has proven a very interesting and informative thread. Many voices which I trust have given many points which explain my original question and given a great deal to take into consideration.
@DeremensisBlue I’m so thankful that you’ve weighed in here as your knowledge and experience leads our way. So now it’s clear to me that I trust your opinion over that of my vet when it comes to chameleons.
My new 12% bulbs arrived last week and have been shoved into storage for now. Perhaps if my plants grow much denser or I feel like installing more ceiling hooks, they’ll be put to use. For now, I at least have spare bulbs for my beardie.
Here is an explanation of the 6% vs 12% that I tried to put into its simplest form for a YouTube video on Panther Chameleon Care. Maybe this can help?
UVB Explanation
Understanding and talking in terms of UV Index is the only way we can have a meaningful conversation about the role of UVB in chameleon husbandry. I am floored that a vet would say knowing your UVB levels is only good for knowing when to change the bulb. Well, then there is a value you are trying to hit if you are measuring to know when it goes below a certain threshold. What is that level and how did you decide on that level? The UVB bulbs we have were not designed for chameleons who can climb up top and get close and personal. They were designed to punch through space to reach a bearded dragon or basking reptile down on the ground. So we chameleon people need to be very aware of UVB and its strength.
I selected UVI 3 as the target level for Veileds and panthers because of experiments done between me, Pete Hawkins, and Johnathan Hill of iPardalis showing these species can fully calcify eggs with out additional dietary vitamin D3. I did a further experiment that showed no difference between offering UVI 3 and UVI 6. These experiments are, by no means, the end of the discussion. If someone wants to use a 12% and offer UVI 8, for example, then fine. But at last understand what you are doing and have a reason in your mind. The problem is when you are an admin of some Facebook group or a vet and you start telling people they should use a 12% sitting on top of a cage "because". Because? What does that mean? Are you following the Ferguson Zones? Did you do some test that says there is some benefit from higher UV Index? Or do you just like the number 12 better? Is there a particular cage condition that requires it?
UVI 3 is just a data point that was proven to work. There is much more work that needs to be done. Me, personally, I will be experimenting with UVB dose and seeing if I can determine a UVI combined with a shorter time than 12 hours for having the UVB light on. But before I tell anyone they should do it I will make sure I have experimented and figured out what the benefit of it is. And then I will share my repeatable experiment for anyone who is interested in exploring it.
So, 12% at 8-9"? I measure UVI 8 to UVI 5 over the year lifetime of the bulb. (There will be variation in everyone's bulb depending on age or how it is driven and everything else. So let's just take that as a magnitude.) Why is this the target if UVI 3 is sufficient? Perhaps we, one day, find that the higher UVB triggers something in their brain during mating season or something like that. Well, then we have something else to consider and experiment with. And once we figure out what UVI that is and at what time of year that needs to be raised then, with a working knowledge of UV Index, we can make it happen. So, this UVI 3 number isn't written in stone never to be questioned. It is a starting point for more experimentation. But let's make sure we use further experimentation to dispute it or justify something else. There has to be a reason to say it should be something different. At least for the sake of people who take chameleon husbandry seriously.
