Just a note: I have a lot of discosomas, [neglecta, greenstripe, purples] that grow and spread like aiptasia in my tank, and they're always butting up against my corals. There's a huge purple that lies right under the tentacles of my hammer, a couple that actually riffle themselves up to rest against the base of my digitata, or within an ace of frogspawn and fox. They seem to position themselves pretty rapidly if leaned upon. We were having a discussion on aggression in the sps forum that produced the following information: pocillopora and stylophora are mild customers; valida and several other sps are hotter; and among lps, watch out for torch and galaxia, and, I'm told bubble, though nothing in my tank seems to respect it much. It got a tentacle onto my poci yesterday [I'm adjusting that] with no damage. So it's hard to say---but because mushrooms can move themselves, I've given up trying to avoid them, and I haven't detectably lost one yet. The discosomas live high under mh, down in the dark, on the underside of rocks, and in holes---they get rocks accidentally parked on them, and get blown by high current and ignored by low, and they still thrive. If I were dealing with rhodactis or ricordia, I'd be a bit more careful, as I think they're both 'hotter' and perhaps less mobile.