Hi everyone - new here!
I recently rescued a crab from a family member… they originally had two but the other one’s shell was empty and his body was nowhere to be found.

There was mold in the food bowl and no water. It was so sad! I brought it home and got it a large tank and filled it with sand and got a water and food bowl… put moss in the water bowl, per the petco employee, and got some new shells and other tank stuff to climb and hide under. I’m not sure how long this crab has been alone but he’s pretty active. I’ve read that they can be lonely when alone so I went and got another one. My original guy was intrigued by the new one and from what I’ve read, his behavior towards the new crab was pretty normal. He lost interest quickly and moved on because the new crab is just in the corner but not buried or active. Should I be concerned? He was active at the store..
I also want to add that the crab I rescued is in the same painted shell that my family members brought him home in… from the beach, TWO YEARS AGO. Is this normal? I have quite a few new shells in his tank now but he seems to take no interest. I’ve read that they like to change shells so I feel like this isn’t normal either. I’m trying to figure this out as I go. I’ve always been a dog and cat person but never thought I would have hermit crabs. When I love and care for something, I want to give them the best. Any and all pointers are welcome