Ack, Xenia is taking over my tank!

[Liv]

I got a tiny tiny piece of xenia from my LFS about four months ago. Since then it as grown at least 10 times it's original size and split three times with lots of branching... Over the past few weeks I've notices many tiny little feathery things growing all over ALL of my rock, throughout the entire tank. I wasn't sure what they were at first but I realized tonight, with a few that have grown faster, that they are definitely xenia. I've been very careful to keep my xenia on a small rock away from the rest and that it doesn't touch anything so it doesn't take over and now it seems it has somehow spawned with waterborn bits or something. I've never heard of this and don't have a clue how to deal with it without harming other corals etc. Has anyone else dealt with this? Any tips or help would be greatly appreciated.