looks like the same type of polyp that i got as a bonus on a chunk of porites....within six months it started overrunning the center of the tank..i tried cutting them out...bad idea,,any little piece grows back and the heads that get away and fall thru the rock attach and start growing. i am going to resort to injecting them with super concentrated calcium to see if it will knock them back.....if it is the same type , be careful, they could take over... the xenia also could overrun. i was warned in the begining to keep them isolated and didn't.. now its a battle to keep them under control