aptaisia(?)anemone

[reefnut]

well i bought a rock covered in button polyps from big als in burnaby.It had this little brown anemone growing out of it.I asked the lady what it was and she told me some kind of anemone.Then she told me it was a good one.So i bought it .Turns out it is bad what can i do to kill it and not hurt the button polyps.