I'd lower it a bit more. Shoot for about 6'' if you can. 6-8'' is the sweet spot for those lights and the useful output drops off quickly beyond about 8''.
I'd stick with the T8 and add the reflector like others said. Seems like at those distances a T5 may be too much.
However, I think what you really need is simply more light. Dragons don't like it dark, and he may be staying close to the UVB simply because it's a main source of light.
I'd say move the T8 closer to the basking bulb, put a reflector on it, and get an additional white light.
The white light can be something like a T8 TropicSun bulb or white and sunlight specified incandescent (may need to be outside the tank to avoid heat issues) or an LED. An LED is a good option if you don't want any extra heat.
I was actually wondering the same thing, T8 or T5...
I'm building two new enclosures for my dragon, and like the OP, planned on doing 24" high, with a 24" T8 10.0 UVB. Every major build video on YouTube, or plans I see for a 4 x 2 x 2, or a 36" x 18" x 24" (LxWxH) all use T8s with a basic fixture from Walmart.
From all the info I was given and researched, you'd have to have your dragon pretty high up to get full benefit of the T8, within 6-8" like Cooper said, which is why I was also thinking of going T5 for that height. I may consider 18 or 20" in height now, and stick with a T8 10.0.
Yeah, it seems like a tricky issue. It's hard to say really without real testing equipment and taking readings, but it seems like this setup puts you right on the line between T8 effectiveness and T5 being too powerful.
There is the T5 5.0 instead of a 10.0 (which is more common). The 5.0 is a bit weaker.
But is also depends on your overall setup. How high your basking spot is, etc. and how much area you have that's shaded from UV but still receives heat.
A T5 HO (10.0) should be between 14" and 20" from the lizard for the liz to get UVB. When mounted inside it's probably going to be a maximum of 20" away, so that means your liz will be getting UVB all the time unless you can provide shade from it, and they will need hot shade, like in the 90+ degree range, so that they don't just sit in the UV in order to be warm.
With it inside it's easy to get your liz too close to it if you aren't careful, but as long as you ensure that your liz isn't gong t be closer than 14" it's probably fine.
Charmander... i do have a reflector. And it is pretty bright in there. When i built the enclosure, i added a fixture on the cool side just in case for the cold seasons (for a CHE) . And i did recently try a low watt bulb on the cool side for a bit extra light, but it made it too hot. But for the heck of it, maybe i will try an LED on the cool side.
With the t8, 8-10" is going to be fine. Any closer than that with a reflector might cause your dragon to avoid the light. t5 would be the way to go with a tall tank....you'll figure it all out.
That sounds good, if it's 10" above the hammock then it will be even less distance to the dragon that is on TOP of the hammock. Do you have other basking areas , branches are especially loved by beardies. Be careful of nail snags in the hammock, some dragons will sprain a foot if they jump off quickly while their nail is stuck. BTW, did you change what you just wrote in your post a minute ago ? As I responded to the one where you described how you attached it to wood so it sits 10" above a hammock ? When I submitted this reply your post was different ?
At any rate, that distance is fine as long as he doesn't get irritated by the light. And if there's a gap above it you might find him hanging out on top of it. I don't think I've ever hung my lights that close in any tank and raised many healthy dragons, even back when all we had was the reptisun 5.0 t8.
And we are both " experts" to a degree. Cooper is quite knowledgeable as an owner and I raised beardies for years + some of mine are even in collections overseas. But experts can have different viewpoints in aspects of care, as long as the animals are healthy, that is the way to measure what is proper care.
One more thing, sorry I didn't mention it above, it's always best if the basking light is lined up next to the uvb so if he were soaking up the heat he would be directly under the uvb as well.
But for the uvb placement, do what you feel comfortable with, which is right in the mix of both Cooper + my recommendation.
Ok so, when i first made this post, the light was mounted to the ceiling, i was told too high, then i lowered it, and it was about 10 inches from hammock, then i was told to shoot for 6-8, which it is in this l last picture
According to my tests, UVI beyond about 8'' isn't enough to be of much use which is why I recommend 6-8'' with a T8. I like to shoot for UVI between about 3-6 in the basking area. I recommend using a T5 in most larger tanks where there is more than 8'' of overhead space available.
The proof is really in the health of the dragons, which is also a test in itself. At 8 ", the Reptisun 5.0 t8 kept my dragons healthy [ this was before I ever owned the 10.0 which didn't come out until years later ] so I go by actual results of the health of the dragon.