You should soak the dry rock a few times to make sure it is clean. You may get a small cycle like slandis3 said. You can get a cycle from many things. Disturbing an established sand bed that isn't regularly stirred, decreasing the amount of bacteria in a tank (which is what you can do with a new tank), adding too much livestock at one time before the bacteria have a chance to balance out. The best thing is to set up the new tank with stuff from the old tank but then slowly transition the livestock to the new tank.