HCA: Hermit Crab Association

My hermit crab buried himself under the water bowl for a little over a month. He's a small guy, but not super small. Well he just came back up, but I'm not sure if he molted. I noticed he went in the salt water bowl, and ate the food I gave him. His skin is really dark and a missing limb he had lost, is now back. He seems really fragile too, but it doesn't look like he grew in size... What is happening???

If he regrew a limb, he
molted. My hermit crab barely grew during his first molt

Yes, if he regrew a lost limb then he definitely molted. They don't always have an obviously growth in size, and even if they do it's often more apparent after a week or so. Feed him lots of healthy foods so he can regain his energy.

they grow a lot in the few weeks following a molt, but if he had to regrow a limb maybe that took a lot of nutrients from growing larger

Congrats on the molt

Thanks for the replies!

I'm really excited about this because the last molt with a different crab was unsuccessful because she tried to molt on the surface. How long should I leave her in an ISO tank before putting her back? I have a large hermit crab who I adopted from someone and she told me that this hermit crab actually ate a molter once! So I definitely don't want to put her back in right away, but I don't want her to be lonely either.

Was your crab isolated during her molt? Was it because she was isolated, then molted, or you isolated her because she was going to molt? If you have enough food and deep enough substrate, it's perfectly safe to let crabs molt in the main tank.
Yes, crabs will eat molters if they find them. That's why crabs need to bury deep and keep themselves safe, it's not just that your one crab in particular is a crazy cannibal or anything. Molters smell delicious to any crab, they smell like fresh soft meat. And any crab who stumbled across a molter would most likely attack and eat him, no matter how much food is available. But if a molter digs down deep, other crabs won't be able to smell them and they can molt in safety.
If a crab does seem to be surface molting, then they probably need to be isolated for their own protection. Otherwise, removing a crab from it's home and putting it in an entirely new environment may stress it out so much he postpones his molt or stops it altogether. Not only that, but they can stress out if they come back up and find themselves all alone. Crabs live in huge groups of hundreds in the wild. They have safety in numbers, and without other crabs around her, your little guy will probably feel vulnerable on her own.
Also, crabs that are different sizes do alot better together then crabs of the same size. That way, they aren't competing for shells I have my four largest crab, including a jumbo, living with smalls and a teeny perfectly fine.

Well she is alone in an ISO because I got 4 new crabs the day after she buried and along with those 4 new crabs I got a new tank, so I put all the other crabs in the new tank and left her in the their old tank where she is buried. She is up now so I don't know when to put her back. She ate a lot the first day but is now slowing down and still playing around in her hole but not covering herself.

Also, I do have crabs of all different sizes, I have a jumbo, 2 very large, 1 medium, 3 small/medium, and 1 small. The one who ate the molter was the same size and took the crabs shell too... so do you think it;s safe to put this molter back in? It's been almost 3 days since she's been up.

If she's eaten all or most of her exo, had a drink, something to eat and is roaming around then she's ready to go into the tank. Just give the new guys tons and tons of protien and maybe put some more shells in the tank as a precaution if it makes you feel better If crabs have lots of protien, shells and space, then they will rarely go after other crabs with the intention of attacking and eating them.
However, crabs the same size do have spats over shells sometimes. My two crabs, Draco and Pinky, are the same size and they occasionally have small spats, but never anything violent. Just keep an eye on them since they're the same size and may occasionally want eachother's shells, but I doubt you'll have many, or any problems The only fights Draco and Pinky have is because Draco is obsessed with Pinky and won't leave her alone sometimes

Haha, alright. Thank you I think I will put her back in her tank tonight. I haven't seen any exo of hers at all, so I guess she ate it. Plus she's been eating her food, checking out shells, and going in the salt water dish a lot. There are 2 other crabs out of the 8 that are her size, but they're hiding somewhere and I've never had a problem with them. I'll make sure to add a bunch of shells their size.