HCA: Hermit Crab Association

Hello,

So we took on a rather large xl PP (Shelly) in July 2023 from a friend who was doing the best he could. She was in a 10 gallon with nowhere to dig. He had her for 1-2 years from someone else who had her in the same conditions. We did a lot of research because we were new to crabbing and got her a 55 gallon with plenty of substrate/sand. She went into a molt that lasted 2 months back in August and she's gotten even bigger. We read that they are social so once she got comfortable we went to get her a friend. While at Petsmart they had 3 small crabs (1 teeny, 1 tiny and 1 small) in horrible shape so we decided to rescue them all 12/4/2023. We set up her old tank and put them in there with some new shells. The largest of the 3 (had holes all over his shell) took a shell and went to molt within 2 days and the other 2 disappeared to molt in their old shells immediately. It's been almost 2 months and I noticed the middle sized one's shell by the food dish and seen him for a second in anew shell but he buried himself again. I haven't seen the other ones. I'm worried about the teeny one the most. While waiting for the new ones to come out healthy we upgraded the big tank with a tank topper (2nd floor) and more climbing and stuff. I saw the middle sized one again this morning and decided to look him over and move him to the big tank with Shelly. We dipped them both in salt water and the little one hid in a tree thing we have in there and we were watching closely for aggression. Shelly is probably 5 or 6 times bigger than the medium one we added. She didn't seem to notice for a bit but them when she got by the tree she rolled off her bridge and headed straight to it, it was a bit hard for her to fit the opening she was trying to enter but did and after about 30 seconds I panicked because I couldn't see what was going on him the smaller one didn't come out so we opened the top and picked up the tree and she was on top of him (we think it's a him) she wasn't rocking or anything so I'm not sure if she was just checking him out or trying to eat him or something. She wasn't latched on to him or anything just on top of him. I'm not sure if she's ever really been around other crabs and if so it would've been quite a few years. We took her off him and dunked them both quickly and then put him in a jar tunnel that she can't get in and set her on the other side of the tank. She went in a hide hole and hasn't came out and he's still in his jar tunnel (we're keeping a close eye. My tank is in our living room) but I'm not sure what to do from here or how to know if she's just curious or if she's being aggressive. I'm hoping that she doesn't have to be a loner crab forever because now I have 3 more crabs (that is if the teeny one survived). Thanks in advance for any advice.

I just adopted two tiny crabs, and put them in with my jumbo after giving everyone a quick fresh water dip. Almost the exact same thing happened - the big guy and one tiny one were in a hide together, I couldn't see what they were doing, so I lifted it up. And Sonny (jumbo) was on top of the newbie - I honestly think there just wasn't enough room in there, and Sonny walked over top of the tiny one.... and in just walking, went right over top like a steam roller LOL. I separated them, and kept an eye on them for a few hours. They've been together for a week, and no signs of aggression.

Oh yay! I'm happy it's working for yours. I checked throughout the night and Shelly was resting on the other side of the tank. I put a food dish in front of the jar opening for the little guy to eat and he would only put a claw out for peanut butter. BUT when I woke up this morning his dish is flipped and Shelly had moved back in her old shell so she could fit in his Jar and he is missing. I have no idea what happened and if he's okay. It's a large convoluted tank and he is tiny. I hope he's okay and she didn't hurt him.

Your little guy could very well be hiding somewhere. There were multiple times in the past week that I checked and couldn't see either one or both of my newbies. But last night, I saw them both at the food dish!

I hope so. I saw Shelly digging around where I thought he was buried so I moved her and looked around in the dirt and still haven't found him. The larger of the 3 rescues (still like 4-5 times smaller than Shelly) came out today in the iso tank but I'm scared to put him in the big tank for fear of what might happen to him. I don't know what to do from here with the other 2. Still haven't seen the smallest one I rescued. It's making me a nervous wreck. I would feel horrible trying to save them just to get them killed.

I haven't found his shell so I'm hoping he's safe somewhere buried.

If your substrate is deep enough, and your tank is not crowded, crabs generally won't dig each other up from molting.
If a crab is buried, do not dig them up or dig around looking for them unless you have an emergency like a flood or bacterial bloom.

He just got done molting. But him and the other 1 kept going back under in the iso tank. I have plenty of substrate but he has to have buried himself because I've looked everywhere else in the tank. I think that's just where he feels safest. I'm just not sure now if I should add the other one now when he comes out again. I seen him today again. I went to change water and he tried to come up under some shells and caved his hole in. I moved the shells and he's took a while but came out and ate and switched shells again.