Not a clue, but sure resembles a baby hellfire anemone (
Thalassianthus aster). I don't know if that's what they are though.
I hate to say this but I would be leery of any biological control. First of all, in my experience, that tends to not work so good anyhow. What seems to work for others never works for me. ("My peppermints ate my aiptasia within 30 seconds of adding them to the tank! No scratch that! They had the aiptasia under control before I even put them in the tank! Yeah yeah!" <---- That's NEVER happened to me.)
But secondly, in your case, I'd be more concerned about whatever eats that -- will probably eat all kinds of other things you'd rather not have eaten.
OTOH, I had a xanthid crab wipe out entire colonies of zoos before I realized what was happening ... and yet he never ate the ONE AND ONLY AIPTASIA in that tank. So things have a way of knowing what costs more and those are the things they'll go to first.
Anyhow point of all this is ... I wouldn't be surprised if manual intervention if your best bet.
Edit: I googled it and hellfire anemone isn't right but the species name looks right. Turns out hellfire is a slightly different looking beast. But yours really do look like that
Thalassianthus aster.