I have found that water is a good start lol. My green stripe is about indestructable. I have had it hot, cold, dropped rocks on it...alot. It is still spreading. I don't do any of these on purpose of course, but it just seems to be the unlucky recipient of all my DOH's!!! It is in a bad place that naturally collects rocks when they fall. Mine was about 3 inches accross when I had PC's and it is now 5 inches or so accross under halides. Really I think a nuclear detonation might have some ill effect, but short of that...water is all it needs.