Best UVB for a Crested Gecko (Do They Even Need It?)

Do crested geckos need UVB?

Honestly, no, not as a hard requirement, and anyone who tells you a crestie will die without it is overstating it. A crested gecko fed a quality complete diet that already contains D3, like the common powdered gecko diets, can do fine with no UVB at all. That is why the animal got its reputation as a no-lights beginner pet.

But "not required" is not the same as "not worth it." The reason experienced keepers add a low level of UVB is that it lets the gecko produce and regulate its own D3 rather than depending entirely on the exact dose in a powder, which quietly removes the risk of over-supplementing D3, a real problem that can lead to an incurable gout-type illness. One keeper who has run low UVB alongside a D3 diet for years reports no health issues at all, which is the point: done at the right low level, it is upside with no meaningful downside.

The one rule: keep it LOW

This is where people hurt their animals, and it is the single most important thing on this page. A crested gecko is a shade species, it lives in dappled forest light, not desert sun, so it needs a fraction of the UV a bearded dragon does. Putting a strong desert bulb, the 10, 12, or 15 percent tubes sold for dragons, over a crestie is genuinely too much.

What you want is a low-output linear T5 UVB tube in the 2.4 to 7 percent range. In Ferguson-zone terms a crestie is a low-UV animal, and keepers who measure aim for a UV index only a little above 1 at the spot the gecko basks. More is not better here; more is a stressor.

2.4% or 7%? Your mesh decides

Once you know you want a low tube, the only real remaining choice is which low tube, and it is not a matter of taste. It depends on what the light has to pass through to reach the animal.

• Black mesh: go 7%. Black mesh blocks somewhere between half and two-thirds of the UV. Put a 2.4 percent tube on top of black mesh and, in keepers' words, it will do almost nothing for the animal. The 7 percent survives the mesh and lands in the right range.
• Silver mesh or no mesh: go 2.4% to 5%. Silver mesh blocks less, around a third to a half, and mounting the tube inside the enclosure blocks nothing. In those cases the 7 percent is too strong and the 2.4 to 5 percent is correct.

The tube can simply sit on top of the mesh, which is how most keepers run it; a UVB tube gives off almost no heat, so it is not a burn risk up there. And distance matters as much as percentage: the further the gecko's highest perch is from the tube, the weaker the dose, so a taller enclosure leans toward the stronger tube.

There is a second variable the mesh rule leaves out, and for a crested gecko it can matter more than the mesh: where the animal chooses to sit. A crestie that spends its days pressed against the underside of the screen is at effectively zero distance from the tube, so the output that would be gentle a foot down is not gentle there. One keeper picked the lower-output tube for exactly that reason, because their gecko lived on the mesh before the light went in, and reports that it carried on sitting directly beneath the tube afterwards. If that is your gecko, read the mesh rule as a ceiling rather than a target and take the lower option.

The corollary is that shade is part of the installation, not an optional extra. The animal has to be able to get out of the UV when it has had enough, which is the whole premise of offering a gradient rather than a level. Keepers running these tubes describe making sure the gecko has cover to retreat into, and a planted or heavily cluttered enclosure does that for you. A bare enclosure with a tube over it gives the animal nowhere to go.

Linear T5, never a coil

Whatever percentage you land on, buy a linear tube, not a compact or coil bulb. This is the same hard rule as for any reptile UVB: coil bulbs light only a tiny patch and are not trusted to deliver safe, even output. Keepers put it plainly, any brand of linear UVB tube is fine as long as the percentage and fitting are right, but do not use compact bulbs. T5 is preferred over the older T8 because it holds output longer, so you replace it about once a year instead of every six to eight months.

On availability, it helps to know the two low-output tubes keepers name are treated as interchangeable at equivalent strength. One keeper recommends a ReptiSun 5.0 T5 HO or an Arcadia 7% in the same breath, and separately reports a visible change in their gecko's activity after adding the ReptiSun. So if one is out of stock, the other is not a compromise, and choosing between them on price or availability is reasonable rather than sloppy.

The brand problem, and what to actually buy

Here is the frustrating part. The tube the crested gecko community recommends most is the Arcadia ShadeDweller, and it is genuinely good. But Arcadia's small UVB kits are chronically hard to buy through normal online retail, keepers routinely report finding them only at a specialty pet chain rather than on Amazon, which does you no good if you are shopping from your couch.

Two honest workarounds. The reliable one is that the Zoo Med ReptiSun 5.0 in a linear T5 is, in the words of keepers who use both, "exactly the same product" as the Arcadia for the price difference, and it is easy to buy. It is the pick most people should make. The other is Arcadia's newer LumenIZE dimmable version, which IS readily available, but it comes with real caveats covered next, so buy it with eyes open rather than as the default.

A warning on the dimmable "LumenIZE" version

Because it is the Arcadia option that is easy to buy, it is tempting, so be clear on what keepers report about it specifically. The LumenIZE is the dimmable ShadeDweller with an app and a slow sunrise-sunset ramp. Multiple keepers describe functional problems: bulbs with unexpectedly short lifespans, odd noises, and unresponsive customer support, with one owner watching replacement bulbs die in as little as two to three months. There is also a credible argument that the headline "slow ramp" feature is more marketing than meaningful, that it does not meaningfully replicate natural UVI changes.

None of this is dangerous to the gecko, and plenty of units work fine. But it means the dimmable version is a gamble in a way the plain tube is not, so treat it as a considered choice, not the safe default. The safe default is a plain low-output linear tube.

UVB changes how you supplement

One thing that surprises new keepers: adding UVB is not just an extra gadget, it changes your calcium and vitamin routine, and getting this wrong undoes the benefit.

The core idea is that UVB lets the animal make its own D3, so you stop force-feeding D3. With a good UVB setup, keepers dust insects with plain calcium, not calcium with added D3, to avoid stacking D3 on top of D3. If your UVB is weakened a lot by black mesh, a small amount of dietary D3 is still fine and even sensible, and a complete gecko diet that already contains modest D3 is generally okay alongside UVB. A low-D3 calcium supplement exists specifically for UVB setups for this reason. When in doubt, err toward less D3, because you cannot overdose UVB but you can overdose a powder.

The bottom line

Give your crested gecko a low-output linear T5 UVB tube: the 7 percent if it sits on black mesh, the 2.4 to 5 percent otherwise, never a coil, and aim for a gentle UV index just above 1 where the gecko perches. It is not mandatory, but it is a real, low-cost upgrade to the animal's health and it makes your supplementing more forgiving.

Buy the Zoo Med ReptiSun 5.0 linear T5 unless you have a specific reason not to, because the more-loved Arcadia ShadeDweller is a pain to buy and the easy-to-buy Arcadia LumenIZE has a real reliability question mark. Then switch your insect dusting to plain calcium, and you are done.