This is a specific conversation about Bearded dragon lighting — UVB and basking done right — ask about yours and get one honest answer for your exact situation.
inparticular.ai
Switching from a coil UVB to a T5 HO is genuinely one of the best things you can do for a bearded dragon — coil bulbs are notorious for producing inconsistent UV output and can't cover a tank properly, so this is the right call. Bad lighting is the most common husbandry mistake with beardies, and incorrect UVB is the leading cause of metabolic bone disease, which often quietly progresses before owners notice anything wrong. To point you in the right direction: what size is the enclosure, what coil bulb are you currently running (brand and wattage if you know it), and how old is the dragon?
It's a standard 40-gallon breeder tank, so about 36 inches long. I've been using a Zoo Med Repti Coil 10.0 UVB. She's just turned one year old.
inparticular.ai
Perfect, that's really helpful. A one-year-old dragon in a 36-inch tank is at a stage where solid UVB matters enormously — she's past the juvenile growth sprint but still needs consistent D3 synthesis to stay healthy long-term. The Zoo Med 10.0 coil has a very small footprint and the UV gradient across a 36-inch tank will be patchy at best. One thing I want to ask before I recommend a specific tube: is the basking spot currently at one end of the tank, with a cooler end at the other? And roughly how high does she bask — is she getting within about 25–30cm of where the UVB lamp will sit?
Yes, basking spot is at the left end, cool side at the right. She usually basks on a medium-height rock, probably about 25–30cm below the mesh top where the light would go.
inparticular.ai
That's a great setup for a T5 HO. At 25–30cm through mesh, you want a 12% UVB tube rather than a 6% — mesh reduces UVB transmission by around 30–50%, so you need the higher output to compensate. For a 36-inch tank, go with the Arcadia Dragon Lamp T5 HO 12% in the 39W / 34-inch size. It's designed specifically for bearded dragons, runs almost the full length of the tank so there's no dead zone, and Arcadia's UV output is well-tested and consistent over its rated lifespan of 12 months. Pair it with an Arcadia ProT5 controller unit — the reflector doubles the usable UVB output, which matters a lot in a 40-gallon. That combination is what most serious keepers and reptile vets in the UK recommend for this exact setup.
Should I mount it inside the tank or on top of the mesh? And do I need to change anything about her basking temperatures when I switch?
inparticular.ai
Mount it on top of the mesh to start — at 25–30cm she'll be getting solid UV exposure at that distance with a 12% tube through mesh. If you can mount it inside the tank directly (no mesh between lamp and dragon), you could drop to the 6%, but the 12% on top is the simpler and safer starting point. On basking temperatures — no, the switch to T5 HO doesn't change your heat requirements at all. You still want the basking spot surface at 40–42°C for an adult dragon, cool side around 28°C, and ambient mid-tank around 32–35°C. Those are set by your basking bulb, not your UVB, so keep that setup exactly as it is. The one thing to do when the new tube arrives: do a full check of basking surface temps with a temperature gun or digital probe, not an analogue dial thermometer — those are consistently inaccurate.
That's really clear, thank you. I'll order the Arcadia Dragon Lamp 12% 39W and the ProT5 unit.
inparticular.ai
Good choice — that's a genuinely significant upgrade and she'll be much better served by it. Set a reminder to replace the tube at 12 months even if it's still lit; T5 HO bulbs lose effective UV output well before the visible light fades, and most owners run them too long without realising. If you notice her basking more than usual in the first week or two after the switch, that's normal — she's finally getting proper UVB and her body is making the most of it.
