Hermit crabs and rocks?!

Hey, Im changing my fish tank into a hermit crab tank right now as we speak.

But, I was wondering if anyone knew if could use the rocks from the fish tank for them. I've got the sand stuff for them too, but can they have aquarium rocks in there as well? I was thinking like a half rocks/half sand thing.

Any ideas?

Sorry this is almost a week later, but yes you should be able to use those!