it's a paly, both of them ive got some i wish i had killed off when i go the rock, they grow quick and take up space that could be used for nicer corals
not that i advocate killing live things, but you can run the rock under really hot water and it will melt them off, how i got rid of my blue xenia and ended up killing some of my zoa's off
I would try and get them off or trade live rock with someone who wants them. you will probably find yourself further down the line wishing you did get rid of them.