These are generally considered pests. But I think it’s an attractive little anemone so wanted to post it for free before tossing it. My tank is small and crowded with coral so can’t take the chance.
Yeah they look really cool in my opinion, I think if I had a bigger tank I’d keep it.They will release and float away, appearing later in other locations. Feeding heavy will cause an infestation of these, or Aiptasia, in my experience.