HCA: Hermit Crab Association

https://photos.app.goo.gl/oxEshooQJN1PecFm7

We just noticed this spot and several very small holes on our hermit crab's shell and I can't find anything that it would be. I just started noticing mites in our tank but from what I have read they are not the bad mites and every if they were mites don't hurt their shells. Is there anything that can damage their shells? She hasn't had any difference in activity and seems fine besides this.

My smallest hermit crab did have a weird reaction a little while ago. I found her out of her shell in the water dish. The shell had fallen into to water dish. I fished it out and put it in the substrat and she got back into get shell by morning. I looked at the video and it looked like maybe she just fell and get shell came off because it was getting too small. I got her some new shells to choose from thinking she didn't like her options and replaced the water source so it was easier for her to get in and out of. She stayed in her original shell. Then maybe 5 or 6 days later I see on the video in the middle of the night she abandoned her shell and took off across the tank to the part of the tank I can't see on the video. I haven't seen her since then. It's been a few weeks. I am really hoping she is just molting in the substrate but worried maybe this has something to do with some issue my tank has??

Finally, I have 2 other hermit crabs that have been under the substrate molting that I have not seen for a pretty long time. Probably more than two months. I have been trying to just not worry because I have experienced them staying under a long time before but with these new things happening it worries me.

The holes may have been there right from when she went into the shell. Do you have other shells for her to choose from? How many?

Crabs do not leave their shell to molt. That she dropped it twice is not a good sign, she may have been too weak to carry it. Hopefully she took a different shell and went underground. If not, she would not have survived a couple of weeks without a shell.

I don't worry until about 4 months or even longer. How are your tank conditions? Heat and humidity readings? How deep is your substrate?

I am starting to think the spots must have been there and we just didn't notice them because she is acting completely normal. That crab is Jelly Bean.

Milk Dud is the crab that I saw run off camera without her shell. It is possible she got another shell and then dug into the substrate because I have a lot of shells in there but I really don't think she did. I wish I had had the second camera then. It was very possible that Jelly Bean was bullying her. Jelly Bean is a lot bigger and would run her over at least once a night. I was concerned about it but wasn't sure if she just did it by accident.

Jolly Rancher came up from molting today so that was very exciting and made me feel better about the health of the tank!!

I have about 6 inches of substrate and keep the heat between 77 & 82. The humidity is between 80 & 85. I have mites pretty bad though so I'm not sure if they are irritating the crabs? When we noticed the shell issue on Jelly Bean, we bathed her to get her mites off her. There were a lot of them but they did just come right off, it wasn't like they are stuck on like it says the bad mites do?!? Then I moved her to my 10 gallon tank. Now, Jolly Rancher is up in the 20 gal but I'm not sure if I should just move Jelly Bean back to the 20 gal because the tank is fine or move Jolly Ranch over to the 10 gallon while I try to do something about the mites? Or any other issue I have? I can't do too much while I have 2 potential molting crabs in the 20 gallon though.

Can you share a photo of the mites, so we can help identify them?

I thought I already had a picture of them but couldn't find one. I did a surface level clean of the tank so I could put Jelly Bean back in there with Jolly Rancher and since then there have been no mites in the food bowl so I can't get a picture but I will keep watching. I am sure they will be back but I guess good news for now. They were very small white ones that I saw mostly in the food bowl but they were on Jelly Bean. When we bathed her, they were on her but came right off. I never saw any stuck to her like the bad kind. I was considering trying the predator mites but having a hard time finding a place to get them. Has anyone tried them before?