How to set up UVB?

Hey, so I got the long, fluorescent reptisun 10.0 24’ t8 high output for my beardie, but I am confused as to where to set it up. I didn’t know at the time that if you get a t8, they say to mount it in the cage itself, but you can put a t5 on the screentop. I’m worried that if I mount my bulb in his cage, it’ll be too close to him (like his basking spot distance would be about 8-10 inches, but there’s another spot on his hammock where it’d be 3-4 inches. Luckily, ]my cage is 48’ long, so I could just set up the uvb to not be over that area but still be over his basking spot. So, i’ve also heard that fine mesh screens block out around 30% of the uvb. But, it seems that the screen on my cage isn’t fine, and the holes are fairly big. If I put it on the screen, would it be ok?

All t8's no matter the screen size really should be mounted inside. Even with fairly large holes it still will block out a decent amount of UVB, and t8 10.0's really don't produce correct UVB past around 8 inches, which is why thats the minimum amount that they can be away from a bearded dragon.

Also mesh blocks out a bit higher than just 30%, more like 40-50% or higher depending on the mesh size.
If you put it on the screen he wouldn't be getting very much UVB at all, you'd most likely risk your bearded dragon falling ill, having MBD, not getting what he needs, etc, as the UVB would be far too weak to give off a correct amount.

If he goes up there on the hammock it's fine, beardies know how to regulate themselves. If they want less UVB they'll go where there is less UVB. If they want more they'll go where theres more.

This set of graphs will help you work out the correct UVB setup , viewtopic.php?f=34&t=235611

Best to aim for 180 - 200 microW UVB flux / sq.cm at the basking spot.

Irrespective of the source, it must be mounted UNDER the mesh if you have a tank with mesh lid , this means MVB, metal halide, T8, T5HO or compact.

I would count on the mesh blocking a minimum of 40% of the UV , essentially cancelling the benefit of reflector hood. See this for how to determine the shading effect for your mesh based on it's weave and wire guage : viewtopic.php?f=34&t=235210&p=1809330#p1809330

I agree that the t8 is safe to place inside, directly overhead within 6-10". As far as the larger holes in some screen as you described that yours has they actually don't block much uvb at all. It's the tight woven flymesh type screen that blocks 40-50%. The type you have would block very little uvb and if the basking areas WERE within 6-8" the uvb going through would still be acceptable.

AHBD":1zyjzrzg said:

I agree that the t8 is safe to place inside, directly overhead within 6-10". As far as the larger holes in some screen as you described that yours has they actually don't block much uvb at all. It's the tight woven flymesh type screen that blocks 40-50%. The type you have would block very little uvb and if the basking areas WERE within 6-8" the uvb going through would still be acceptable.

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This^
T8 are best off with out a screen. If you have a good reflector for it, you can get away with having it outside the screen if you have wide holes in the mesh. Generally I wouldn’t reccomend it, if you can set it up otherwise. As long as you set things up so the dragon is no closer than 6” it should be fine.

For reference :
Window screen blocks about 50% of UVB, exoterra screens ablock about 35%,

The screen blocks a bit less than that, the 5mm screen [ Exo terra type ] would only block 15-20% according to the uk.uvguide.

http://www.uvguide.co.uk/fluorescenttubemeshtests.htm

Hm, I wonder if the larger exo-Terra’s have larger screen, I don’t recall them being so big. If what OP has is actually 5mm or larger then yeah, very little loss in that. My widest mesh is 3mm and is 35% blockage. My little exo-terra is finer than that.

I see if you Google it that they do come in different sizes of mesh. So under the screen is probably best, especially if there's more than 8 inches to the basking bub. With the t5 it can be put on top of the screen.

Thank all of you guys for helping me out!! I luckily found a way to mount it inside of his cage, so I will plan on doing that. Thanks again!