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Question about UVB for a big tank

PostPosted: Tue Jan 21, 2020 8:12 am
by timberwolf
I've been receiving some conflicting information regarding how much UVB I need for my bearded dragon setup. Her home is a 125 gallon aquarium that is 6' long, 18" deep, 18" wide. I have a grow bulb on the cool side that spans about half of the tank. Over her basking spot is a ReptiBasking bulb and a ReptiSun 10.0 UVB coil bulb. She can be within 6-12" inches away from the bulbs, depending on how high she climbs. My question is do I need more UVB? Should I have a UVB tube bulb located over the cool side as well, so no matter where she goes she's under UVB? If so, what type do you recommend and where's the best place online to get it if I need one? She seems really healthy and is about 10-11 months old. Appreciate any input you may have. Thanks!

Re: Question about UVB for a big tank

PostPosted: Tue Jan 21, 2020 8:22 am
by ComicBookMama
The advice I've been seeing on this forum is that the UV should cover about half the tank, so she can get out of it if she wants to... but manalive, that's one long tank! You must have one seriously happy dragon!

The only problem I see with your setup is that you said you've got a coil bulb. Most of the veteran posters I've seen address this will tell you that the coils really aren't the best for dragons - that they don't give out enough UV, and some are bad for their eyes. You'll want to go over to a tube bulb, either a T5 HO or a T8. I think the T5 HO bulb can be on top of the screen, but the T8s aren't as strong and need to be mounted inside the tank, 6-8" from the basking spot. I've got a Reptisun 10.0 T8 in my tank, but a lot of folks will recommend the T5s because they're really a lot stronger.

Re: Question about UVB for a big tank

PostPosted: Tue Jan 21, 2020 8:32 am
by timberwolf
Thank you! Yeah, I kept African Cichlids for almost 20 years. Couldn't let the empty tank sit around so when my son started getting interested in lizards I told him we could make the empty tank into a lizard habitat. It's been a fun experience so far. I was concerned about the coil bulb but left it in place because it's approaching it's 6 month lifespan anyway. When it came time to replace it I was thinking about swapping it for a tube light instead. I'm just wondering if one tube light to cover about half of that tank is enough or if the UVB should cover the whole thing. I also wondered if it would eventually harm my plants if I had too much of it.

Re: Question about UVB for a big tank

PostPosted: Tue Jan 21, 2020 8:38 am
by KarrieRee
Here is some info Brandon posted not long ago on coil UVB's I recommend you get rid of the coil and get a 36" fixture since your tank is 72" long ----

Can anyone tell me what is wrong with UVB coils? I currently have an exo terra uvb150 coil bulb for my juvenile beardie and ive had it since october....
i was planning on upgrading the bulb before I heard the unspecified negativity about them- im going to the pacnwrs (reptile show) tomorrow and i'm planning to purchase a 48 inch strip and a t5 ho zoo med uvb 46 inch bulb for him, hang it inside the 4x2x2 tank so he gets the most out of it. I took him to the vet on the 11th and his calcium levels were all good on a blood test

Some coils are strong enough, the majority are not.

So firstly, there is the strength issue. You want to provide a certain level of UV at the basking site and throughout the tank, and that is very difficult to do with a coil unless you have a very strong coil.

But even if you do have a strong coil, the way the bulb outputs, it "shines" a cone/beam of UV down into the tank which leaves the majority of the tank UV-less. You can imagine how a tube fluorescent instantly would solve that issue.

Not to mention, the tubes are generally much stronger, which makes it much easier to provide the proper amounts of UV.
So recommended is the Reptisun 10.0 T 5 HO or the Arcadia 12% or 14% bulb - the 14% bulb would also be good for the tank as it is stronger--- I am guessing around 24" from basking area - you can check this website for distance on this bulb -- www. ... n-baskers/

Re: Question about UVB for a big tank

PostPosted: Tue Jan 21, 2020 9:30 am
by Claudiusx
Hi there,

In such a long tank, and with a coil bulb, you really are only providing UVB to about 6 inches of that 6 foot long tank.

The grow bulb you have does not output UVB at all. And, the coil bulb you have, you can imagine only outputs a quite narrow beam of UVB. Not only that, but most coils are vastly underpowered, and you likely aren't getting even close to the UV requirements of your dragon in a tank that size with your bulb.

At 18 inches tall, I'd go with the reptisun 10.0 HO or the arcadia 12%. These are both T5 sized bulbs, so you will need a t5 fixture to house them. You want the bulb to span 1/2 - 3/4 of the tank, so you will most likely want to go with the 46 inch version of the bulb.

And then, you will want your basking surface to be around 12 inches or so from the bulb unobstructed. This will provide you the proper UVI level for your dragon while it basks. While the rest of the length of the bulb, will provide a UV gradient over to the cool side, just like you want with your temperatures.


Re: Question about UVB for a big tank

PostPosted: Tue Jan 21, 2020 9:33 am
by timberwolf
Thanks very much for the replies. Very helpful!