Well, the whole purpose of the cycling process is, for one, to allow bacterial colonies to develop. During this time as the LR experiences die off, ammonia will rise and then start to drop off as nitrite starts to rise and then eventually drops off. Once there are no traces of ammonia and nitrite in the tank, then it is said to have been cycled. This usually takes about 6-8 weeks in most cases, but varies depending how much die-off you experience. So the answer to your question if anything in the rock dies, is usually yes (that is if the rock you received isn't already completely cured) When you buy LR and it is truely cured (which I've honestly never seen) and doesn't experience any die-off, you will usually have to add a few hardy damsels or feed the tank, to create some sort of bacteria to cycle your tank and develop these same bacterial colonies. A good thing to do when cycling is to test the waters parameters before adding the rock (ammonia, nitrite and if you want nitrate) and then test it every couple of days to see if you see an increase in any of these. If you do, then your rock is experiencing die-off and you are well on your way to cycling the tank. And like I said, once these parameters (ammonia and nitrite) return to 0, then your tank should be safe to say is cycled.