Hi, thank you! Rocks are really nice man, I've got 4 crabs with the rocks that I found but they're very very tiny and I can't catch them yet even with traps. I'm not sure I think I've one Porcelain crab, one Stone Crab and two Gorilla crabs. Last three are bad crabs, but they're so small that at this moment it's not a problem. I like to run the system with large amount of hermits, I've around 12 of them in the tank, small one. So every time I try to catch these guys with a trap, all what I'm getting it's a bunch of hermits.
You don't need to do anything with the rocks, just put it in your system. These are real live rocks.
Good luck!