Bearded dragon lighting for ADV dragons

Bad lighting is the most common husbandry mistake with bearded dragons — incorrect UVB or basking temperatures lead to metabolic bone disease and chronic immune suppression that owners often miss until real damage is done. With a dragon who already has adenovirus in their history, getting the lighting exactly right matters even more, because a weakened immune system has less tolerance for the ongoing low-grade stress that poor UVB or inconsistent basking causes. To give you the most useful advice: what size is the enclosure, what UVB and basking bulbs are you currently using (brand and wattage), and how old is your dragon exactly?

Good that she's been stable — that's a solid sign her immune system is coping. The T8 Reptisun 10.0 is a reasonable bulb but it has a real limitation in a 4x2x2: T8 tubes put out lower UVB intensity than T5 HO tubes, and in a wooden viv the basking spot is often quite high off the floor, which reduces the UVB dose reaching her skin further. For a dragon with any immune history, you want her UVI levels in the basking zone to be consistently in the 4–6 range without guesswork. What height does she typically bask at from the tube — roughly how many centimetres between the bulb and her back when she's on the basking platform?

At 35–40cm a T8 10.0 is delivering a UVI of roughly 1.5–2.5 at best — that's meaningfully below the 4–6 target for an adult bearded dragon, and it's the kind of chronic mild deficiency that quietly taxes immune function over months. For a healthy dragon it's suboptimal; for one with ADV history it's a real concern. The basking bulb situation also needs sorting — an unbranded bulb from a viv bundle is unlikely to be a true halogen flood, which means her basking temperature is probably inconsistent and her surface heating less effective than it should be. Here's what I'd recommend: switch her UVB to the Arcadia T5 HO 12% Dragon Lamp in a 39W size for a 4-foot fitting. At 35–40cm it consistently delivers UVI 4–6, it's the most rigorously tested bulb available in the UK for bearded dragons, and it runs cooler and more stably than T8 tubes — no flicker stress, which matters for a cautious immune system. Pair it with the Arcadia 100W Deep Heat Projector for basking; it heats surface and tissue the way solar radiation does, reduces the energy her body spends thermoregulating, and has no visible light output so it doesn't disrupt her photoperiod. The combination gives her the most naturalistic, low-stress thermal and UV environment you can offer without overcomplicating things.

Stick with the 12% — dropping to a lower percentage like 6% would put you back in the same underexposure problem you have now, and UVB deficiency is a far more documented stress on bearded dragon immune systems than appropriate UVB exposure. The 12% at 35–40cm sits in the Ferguson Zone 3–4 range that wild bearded dragons occupy during peak basking, and that's exactly what her biology expects. What you want to avoid is UV overdose from getting the tube too close (under 25cm), not from using the correct percentage at a sensible distance. One practical note: replace the Arcadia tube every 12 months even if it still looks lit — output degrades significantly before the bulb fails visibly, and consistent UVI matters more for her than for a healthy dragon with full immune reserves.

Those two changes will do the most meaningful work. If you want to go further, add a digital thermometer with a probe to verify her basking surface temperature is hitting 40–42°C — surface temp under the DHP, not air temp. And if you don't already have a UVI meter, the Solarmeter 6.5 is the gold standard for checking her actual UV exposure after installation; it removes all the guesswork and you only need to buy it once. But honestly, the Arcadia T5 HO 12% and the DHP are the changes that will make the real difference for her. She sounds well cared for — these upgrades will give her system everything it needs to stay stable.