that seems to me more like majano which peppermint usually won't consume those.however, they are not as bad as aiptasia.They will not populate as fast as aipasia.Mine was left alone in my main tank with 5 peppermint, and after 5 months it still there and didn't do any harm.If it does out of control maybe do a Kal injection and it should kill it.
try this link=) hope this helps
http://www.wetwebmedia.com/ca/cav1i3/aiptasia_impressions/aiptaisia_impressions.htm