I haven't seen them dislodging heads for the past 2 years actually... they spread by moving onto other rocks.... much like shrooms. So if you just keep it away from other rocks, it won't spread like weed. Well, at least this one hasn't since I have it in my tank. I am still keeping some xenia in my tank... this piece is an extra one I have. They can be aesthetically pleasing actually if you don't let them spread all over your tank. My other rock has xenia on top with some green rics at the bottom and I think it's beautiful. It's also a good beginner's coral.
