HCA: Hermit Crab Association

One of my crabs was out of its shell this morning which wasn't a huge surprise bc I've been thinking she was too big for the one she was in anyway. My concern is great now bc it's evening and she still hasn't chosen a new shell. I have at least 30 shells in the 29 gal tank she is in and at least 6 or 7 appear to me to be good options for her. Tank temp is 74 F, humidity is 80%, salt and freshwater pools available at all times with bubblers built in, extremely varied diet full of meats, veggies and fruits as well as calcium. Substrate is a mix of sand and coconut fiber. I am just completely stumped and this particular crabby happens to be the family favorite so I am desperate to help her anyway I can.

Any thoughts or suggestions would be greatly appreciated

A naked crab is always an emergency. They should never be willingly running around naked.

How long have you had her? Do you know what species of shells you have, and if not can you post a picture?

For now, get her rinsed off in the freshwater bowl and put her in an empty container with no substrate - like a tupperware or clean margarine container - and then also rinse off a few shells that should be her size and put them in with her. Leave her like that inside the tank for maybe a half hour and see if she reshells. The idea is to give her nothing to do other than shell shop. With luck she'll put one on by herself.

I'm new to this forum and can't seem to figure out how to share a pic. I have had this particular crab for about 6 months and she changed shells as soon as she came into my care without issue. I have rinsed her and several shells off in de chlorinated water and have placed her in a plastic container and turned out the lights...giving her some time to shop and anxiously hoping she chooses a shell

Her abdomen doesn't look right, that's why she's naked. It's too swollen. It could be organ failure or she could be about to molt. It's so hard to tell with these guys! If she doesn't put anything on in about a half and hour, I would try to slide her into a shell and see if she keeps it on. The green one is the best choice of what you have for her, but it might still be too heavy. If that's the case, use the one that's off to the right - the lightweight one with faint striping. If it is a molt she's going to do it soon.

Ok, so we are about 30 hrs from when I discovered Luna outside her shell. Even after trying the method of putting her in the container with nothing but shells, she still hasn't gone in one. I have manually put her into a couple of different shells but she jumps right out. Her abdomen does look very large to me but I can't find any external injuries, nothing that looks like parasites and at this point have just placed her in my 10 gal ISO so the other crabs won't hurt her. I'm misting her with water periodically to keep her from drying out but am at a loss for anything else to try.

There really isn't anything else. Make sure sure her bowls are deep enough to submerge in and that the saltwater is made with Instant Ocean so she can soak. That might get her comfortable. Temp should be around 80 and since she's naked I'd boost the humidity up to at least 90% for now. Either time is going to let her correct this or.... I'm so sorry.

I appreciate you trying to help. I'll let you know what happens.
Still clinging to hope but prepping for the likely outcome...

Sadly Luna passed away last night. She hung on for several days but just didn't make it. Just hoping it wasn't something I did or didn't do. Upgraded my hygrometer/thermometer before deciding to do something about the temp and I'm glad I did! Temp is reading at 81 and humidity at 78%

Thanks for all the suggestions and help.