Sorry to jump on in your post here, but I have a similar concern w/aptasia. I have something that I think is aptasia, but does not match any of the pics searched on the web. I will be posting a pic soon. It came in on a anemone crab shell and one day dislodged itself from the shell and made its home on a rock. I have some mushrooms, star polyps, and button polyps and it hasn't attacked those. Can I assume that it not then?