mushrooms

What makes mushrooms all at once decide to leave their rock or move around to other places?   I have several nice red ones and they are moving off the home rock for other places.  They were not crowded or anything like that.  One came off altogether and I promised it to Will.  I would rather they not go into hiding under the shadows of other things.

I once had a very small "bug" in my tank, it looked like some sort of a clear spider and was about 3-4mm in size.  It would cut the mushrooms at the base and carry them off somewhere else.  Well, everywhere one was cut a new one would grow in it's place .  I just thought they were self propogating like crazy.  When I woke up one morning and flipped the lights on I saw it holding one at the very top of the rock pile.  Not very long after that, they stopped propogating as often as they were.  I think this "bug" has died because I haven't seen it for some time.