My tank is full of rocks - all shapes and sizes. I pick up new ones when I'm out and about - usually river rocks and other than rinsing them off and doing a soak in the tub to loosen and scrub off any soil / bugs, I just plop them into the cage. I usually let them soak for 24ish hours to make sure there are no bugs in the cracks to come out if it is a rough rock. If you have a glass tank you'll have to be a lot more careful and choosy so you don't crack the tank.