They are most likely that anenome. Are you familiar with aiptasia? Some of the same manual methods will work on these little fellows. I am not familiar whether or not biological controls (copperband butterfly, peppermint shrimp) will work on these little fellas. However, injecting with kalk and boiling water should work. Do not scrub them off in your tank. All of the little pieces will form new colonies, and I don't think tweezing them off will work either. They will just resprout.
Fight the good fight.