Bearded dragon lighting with a crested gecko

Running a bearded dragon and a crested gecko in the same home is actually a really common setup — but it does create a genuine lighting conflict. Bad lighting is the most common husbandry mistake with bearded dragons: incorrect UVB or basking temperatures cause metabolic bone disease and chronic illness that owners often don't notice until real damage is done. At the same time, cresties are nocturnal and sensitive to bright light, so a poorly timed or poorly positioned rig can stress them badly. To point you in the right direction: what size is your dragon's enclosure, what UVB and basking bulbs are you currently running (brand and wattage), and how old is the dragon?

That T8 10% is the root of the problem for your dragon, and the proximity is almost certainly stressing your gecko. T8 tubes have low UV output and degrade fast — by month three they're often putting out a fraction of what's on the label, even if they still look bright. An 18-month-old beardie in a 4x2x2 needs strong, reliable UVB across the full length of the basking zone. Before I give you a specific recommendation — are the two enclosures side by side on the same surface, or is there any separation between them? And is the gecko's terrarium covered on the side facing the vivarium?

Right, that plain glass is letting the light flood straight in and that will absolutely disrupt his sleep cycle and stress him. Here's what I'd do across both problems at once. For your dragon, replace that T8 with the Arcadia T5 HO Dragon Lamp 14% — it's a 12% UVB tube in a high-output T5 format, designed specifically for deep wooden vivariums in the 4x2x2 range. It runs the full length of the basking zone and gives consistent, measurable UVB for 12 months. Pair it with the Arcadia controller unit so you can run a proper photoperiod — lights on at a set time, off at a set time. That's the key move for your gecko: a strict 10–12 hour light cycle on a timer means the dragon's light is never bleeding into the gecko's active nocturnal hours. Also put a sheet of opaque black card or foam board on the side of the gecko's terrarium that faces the vivarium — cheap fix, immediate improvement. Your 75w halogen basking is fine for now if the hot spot is reaching 40–42°C; just verify that with a temp gun.

Go and get a temperature gun — it's non-negotiable. 'Feels warm' is not a measurement, and a basking spot that's 35°C instead of 42°C is contributing to the same slow-burn illness as bad UVB. The Arcadia ProT5 Dragon Kit comes as a complete unit with the reflector and controller, so yes, everything you need is in the box for the lighting side. Search for the Arcadia ProT5 Dragon Lamp Kit 14% 1.2m on Amazon UK — it's the right length for a 4-foot viv. Fit it to the ceiling of the vivarium above the basking log, not mounted to the side, and keep the dragon within 30–40cm of the tube to hit the correct UV Index. Set your timer, card off the gecko's side panel, and check that basking temp this evening.

Two things for the long run. First, replace the Arcadia T5 tube at 12 months regardless of whether it looks fine — UVB output drops before visible brightness does and there's no reliable way to judge it by eye without a Solarmeter. Second, cresties do better with a temperature drop at night, around 18–22°C, so if your shelf space means the dragon's night heat is warming the gecko's terrarium, you may want to rethink the layout over time. A small USB fan circulating air between them can help with that. But get the T5 kit, block that side panel, and check the basking temp — those three things will make a big difference immediately.