Zebra Hermit Crab behaving oddly

Hi

I bought a Zebra Hermit crab a little over 3 weeks ago and its been very active moving all over the tank and switching shells sometimes twice a day, but suddenly then 2 days ago the crab sat in a little cave like area under a rock and stopped moving for almost the whole time. I picked up the shell and moved it yesterday thinking he was stuck, but after i moved him, he got up and moved right back into the same spot and then stopped moving again. I don't really get it but maybe someone else has observed this behavior in hermit crabs?

None of my other fish(1 yt damsel, 2 clowns, 1 lawnmower blenny) are showing any issues.

Thanks in advanced!

Water levels:
Ammonia: 0
Nitrite: 0
Nitrate: 3-5 ppm (I did a 10% water change afterwards but that is still far below any dangerous amount.)
Ph: 8.2-8.3
Salinity: 1.023

 

He's probably just molting, give him some time.

 

I would say molt as well.. especially if he has been switching shells around.

 

phew! That explains why he's in a large shell compared to his size. Thank you for that news! k+

 

More then likely about to shed its exoskeleton, give it a few days and it should be just fine.