If it's a hermit, then just about any shell should do. You can probably go to your LFS and ask for some empty snail shells. We have them all the time and I usually make up betta cups with an assortment of them to sell for a $1. Just dump them in there with him and let him choose.
That's the smallest I've got. And no, I'm not sure about the type of crab it is. He was much smaller and I moved him in a huge shell over to one of my nano tanks. After 3 months, he decided to venture out. Until now I've only seen his big claw.
I'm not sure that's a hermit. The one's I've seen out of their shells look much different, like creepy naked spiders It almost looks like a tiny pistol shrimp to me. Pretty cool!!
I am thinking shrimp too. I've seen my crabs switch shells (wish I could find the video I made long ago of it!). and it looks nothing like that. So yea.. I think a shrimp
I looks like a pistol shrimp to me.Does it exhibit any rubble moving behavior? Sometimes one can hear their snapping noise .Even for a distance from outside the tank.