HCA: Hermit Crab Association

I understand Strawberries need UVB. My question is, what is the secret to keeping humidity in if you use a lamp placed on a screen top? I know to wrap the screen top in plastic but is there another way to use uvb lamps and seal in humidity? I’d like to use a glass top, but I know uvb can’t get through it. Any advice is appreciated.

New here but are you using a coil compact or a tube. You could use zipties to place it inside the tank if a tube and uvb doesn't get that hot. That is what many herpers do. They do have sockets that can be installed for coil/compact bulbs.

You’d be looking at covering anything that isn’t covered, so the whole lid except the lamp.

Even so, you’ll still have a gap so you may need extra water inputs such as misting, otherwise you’d have to mount a lighting fixture inside the tank where the crabs can’t get it.


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Do strawberries in fact need UVB. I've read it's not proven that purple pinchers do.

If you do mount one, it's got to be inside the tank with nothing but air between the bare bulb and hermit crab.

Those that have had their straws the longest have used UVB. It's not a guarantee, and there's no proof, but straws have such short lifespans in captivity that it may give them another couple of years and is considered beneficial.

JTKermie wrote:Do strawberries in fact need UVB. I've read it's not proven that purple pinchers do.

If you do mount one, it's got to be inside the tank with nothing but air between the bare bulb and hermit crab.

Anecdotally straws seem to live longer in enclosures with UVB, but enclosures with UVB tend to be better in general so it’s hard to draw concrete conclusions.


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I want to thank everyone for their replies on my post. Good advice all around. Going to go with wrapping screen lid and zip tying a uvb lamp fixture to the screen.

With glass tops I've seen it recommended you silicone a plastic fluorescent light fixture to the inside of the glass. The lamp/fixture style really depends on the distance between the bulb and your hermit crabs. If it's a big distance, UVB doesn't make much sense to me. It's not going to reach them anyway. Then you have to contend with changing bulbs every ~6months because the UVB fades from day one.

Back when I ran T8 and T5 fluorescents on my planted aquariums I used to contend with this. The PAR/PUR radiation they give off for plant growth fades pretty quickly. The bulbs still light up and look good to the human eye, but they're not doing their thing for the plants. Same concept with UVB bulbs.

JTKermie wrote: ↑

Sat Oct 02, 2021 1:02 pm

With glass tops I've seen it recommended you silicone a plastic fluorescent light fixture to the inside of the glass. The lamp/fixture style really depends on the distance between the bulb and your hermit crabs. If it's a big distance, UVB doesn't make much sense to me. It's not going to reach them anyway. Then you have to contend with changing bulbs every ~6months because the UVB fades from day one.

There are a lot more options these days! With percentages up to 14%, distances 21 inches away or more can still get full blaring UVB. (With crabs it's important to factor in how close they can climb up to the bulb and use that as a basis. 5.0 or 6% or 'shade dwelling' is usually perfect for them.) And the better brands of T5 will last a full year now, like Arcadia. The really great thing is that crabs won't have health issues if the UVB does fail for some reason, like reptiles do, so there's little risk.

wodesorel wrote: ↑

Sun Oct 03, 2021 8:59 am

There are a lot more options these days! With percentages up to 14%, distances 21 inches away or more can still get full blaring UVB. (With crabs it's important to factor in how close they can climb up to the bulb and use that as a basis. 5.0 or 6% or 'shade dwelling' is usually perfect for them.) And the better brands of T5 will last a full year now, like Arcadia. The really great thing is that crabs won't have health issues if the UVB does fail for some reason, like reptiles do, so there's little risk.

Good to know. Again, I still struggle with the whole UVB / hermit crab thing because some sources say you need it, others say you don't.

I only have experience with T5's for fish/plant keeping. I completely got away from them because it's difficult and expensive to source quality fluorescent tubes these days and the fixtures/electronics are junk. Manufacturers have largely gotten away from fluorescent, transitioning to LEDs. Aside from one twin tube 48" T8 I still use, my remaining planted tanks use LEDs now,

Ugh, I agree about the T5 fixtures. I burned out the ballast on three newish ones this past year and there are no replacement parts available. I was ticked!! Ended up buying a secondhand marine T5 HO fixture from a friend and it's been holding up well at least. I have two turtles and some golden geckos that need it, so I have to run a few lamps. In fact, it's time for yearly replacements and I'm having trouble finding stuff in stock! Another fun bit to deal with.