Best Chameleon UVB: Which Tube, How Strong, and How Far Away

Linear tube, never a coil

The bulb has to be a long straight tube, T5 HO or T8, running across the top of the screen. Not the little spiral compact that screws into a dome. Keepers are blunt about this because the compacts have a track record: they've been linked to photokeratitis, the eye inflammation that makes a chameleon sit with its eyes closed, and the standard advice when someone posts a photo of one is to replace it immediately, whatever animal is pictured on the box.

The other reason for a tube is coverage. A chameleon needs to choose its own exposure, moving up toward the light and back down into shade through the day. A single point source lights one spot. A tube running most of the cage width gives your animal a gradient it can move along.

6% or 5.0, and no stronger

For veiled and panther chameleons, buy 6% if you're going Arcadia or 5.0 if you're going Zoo Med. They're roughly equivalent. Skip the 10.0, the 12%, and the 14% Dragon tubes: those are desert-species output, they're named repeatedly as an eye-burn risk for chameleons, and the extra strength buys you nothing your animal wants.

If you already own a tube and can't remember what it is, look at the endcap. Anything unmarked is worth replacing rather than guessing, because you cannot judge UV output by eye or by how bright the cage looks. Pair it with a proper screen enclosure, since glass blocks UVB entirely and a glass tank changes this whole calculation.

The T8 camp, stated plainly

We've recommended T5 HO, but a sizeable and knowledgeable part of the chameleon community prefers T8 5.0, and they have a fair case. T8 is weaker, which means it can sit closer and sits more forgivingly straight on top of the screen, and several long-time keepers call it their default for exactly that reason. The counter-argument, and the reason we land on T5, is that T5 punches through mesh better and T8 availability has been getting patchy. Either is defensible. What matters is that the distances differ: the 8 to 12 inch figure below is for a 6% or 5.0 T5 over mesh. If you run a T8, it needs to be closer than that, not further, or you'll under-dose toward metabolic bone disease.

Distance: 8 to 12 inches to the animal, not the branch

Mount the fixture above the screen and keep 8 to 12 inches between the tube and the top of your chameleon when it's basking. Measure to the animal, not the perch: an adult veiled's casque adds roughly three inches, and keepers point to unaccounted casque height as a common cause of burns. So a perch 8 inches down can put a big male's head at 5 inches. Add about three inches to your perch distance for an adult and you're in the right place. The range assumes mesh in the way, which costs roughly 30 to 40 percent of the output. We'd start at 10 inches to the animal and adjust.

Closer is where the trouble is. The failure mode is a branch or vine that lets the animal climb up near the tube, so check the cage from your chameleon's point of view, not from outside the mesh. If it can get its head within a few inches of the fixture you have two options, and lowering the branch is only one of them: plenty of keepers instead sit the fixture on blocks a few inches above the screen, which buys distance without giving up the top of the cage. Offsetting the tube to one side rather than centring it also helps, since it lets the light reach the animal's flanks and leaves a shaded side to retreat to. If you have a Solarmeter, aim for about 2 to 3 UV index where the animal sits. Metered readings at these heights usually land between roughly 1.7 and 2.6, which is right. Never move the tube closer than the distance floor to chase a higher number, because that is exactly how animals get burned. Without a meter, follow the distance and don't improvise.

The UVB tube is not your heat source

Put your hand under a T5 and you'll barely feel it, and that surprises people who assume one fixture does both jobs. It doesn't. UVB drives vitamin D3 synthesis so your chameleon can use calcium; warmth for digestion comes from a separate basking bulb over the same end of the cage. Run both. Veileds and panthers generally want a basking spot in the low-to-mid 80s F, and panthers on the cooler side of that. Don't try to fix a cold cage by moving the UVB closer.

Replace it before it dies

Fluorescent UVB output drops off well before the tube stops lighting, so a bulb that looks fine can be doing very little. Manufacturers say 12 months; plenty of keepers swap at 6, and some go sooner. We'd put a piece of tape on the fixture with the install date and replace between 6 and 12 months. Some keepers go as short as 6 on principle. A meter is the only way to know for sure, though it costs several times the tube and experienced keepers are split on whether it's worth it, with some saying they don't fully trust their own readings. Buying used is common.

Worth knowing before you shop: a bare replacement tube often costs nearly as much as a whole fixture-plus-bulb kit. If you're starting out, buy the kit. If you already own a good hood, just buy the tube and ignore the pricing weirdness.

What we'd buy

For a standard 24 by 24 by 48 cage: a T5 HO fixture with a 5.0 tube, sat above the screen, with the animal's head about 10 inches below it when basking. A separate basking bulb for heat. The install date written on the fixture in marker. It's a cheap setup to maintain and it's what we'd run.