Upgrading bearded dragon UVB lighting

Getting heating and UV lighting right is genuinely the single most important thing you can do for a reptile — the majority of common illnesses, from metabolic bone disease to respiratory infections, trace back to incorrect temperatures or inadequate UVB. So if you're upgrading your UVB setup, you're already doing the right thing. To make sure I point you in the right direction: what species are you keeping, what size is the enclosure, and what do you currently have running for heat and UVB?

You've heard right — the Repti-Glo coil is one of the weakest options for beardies and a 4x2x2 really needs a linear T5 to get proper UVB coverage across the whole basking zone. For an adult bearded dragon in that enclosure, the bulb I'd recommend is the Arcadia Desert 12% T5 HO, 39W in the 34-inch length. It's specifically calibrated for desert species like beardies and produces the high UVI levels they need — around 4 to 6 in the basking zone — which a coil simply can't match. One important thing: what height is your basking platform from the bulb? That changes how you position it.

That's a good distance for the Desert 12% — at 25 to 30cm you'll hit a solid UVI of around 4 to 6, which is exactly where an adult beardie should be basking. Any closer and it could tip too high; any further and you lose the benefit of the upgrade. One thing to keep in mind: this bulb should run inside a reflective T5 fixture, not just a bare holder — Arcadia's own ProT5 controller is the standard pairing and makes a real difference to output. Also, you'll still need a separate basking spot heat lamp alongside it — the T5 provides UVB and some ambient light but doesn't replace your heat source. What are you currently using for basking temperature?

That's spot on for a bearded dragon — 40 to 42°C at the basking surface is exactly right. So your heat setup sounds solid; it's really just the UVB that needed the upgrade. To summarise what I'd get: the Arcadia Desert 12% T5 HO 39W tube, paired with the Arcadia ProT5 reflective controller in the matching 34-inch size. That combination will transform your beardie's UVB exposure compared to the coil. Replace the tube every 12 months even if it's still glowing — the UVB output degrades well before the visible light does.

Yes — worth doing a short introduction period since your beardie has been on a weak coil and isn't used to proper UVB intensity. For the first week, either raise the fixture a little higher or reduce the photoperiod by a couple of hours so he can adjust. After 7 to 10 days, move to your normal positioning and a full 12-hour cycle. It's a small step but it avoids any stress from the sudden jump in UVI. After that, just run it on a 12-on 12-off timer and you're set.