Is it good or bad and how sure are you?aiptasia anemone
If you can remove the rock with ease you cold just burn it off with a cigarette lighter.
ThanksTried to reply from my phone earlier that never works out for me.anyway from what I can tell from your pictures. It could vary be a serpent star.I've got one that looks similar but mine has to be a foot long or better.I use a feeding stick that looks like a shish-ka-bob stick or long tooth pick to feed it.I find it easiest to feed it at night. As long as it not a green serpent I think your safe.mine hasn't bothered any corals or fish. Good luck with it