Looking at it to me it doesn't look just like any aiptasia I have but I believe it is some type of pest anemone. You can get rid of it the same way you do aiptasia vinegar, lemon juice, pickling lime, or aiptasia x or one of the other things that is suppose to kill them. I have several in my tank that never die completely they just come back bigger. If you can get real peppermint shrimp that is the best way to go since they can usually get where our hands can't go. If you have a coral banded shrimp then don't get any peppermint shrimp chances are they will be killed before they can do their job.