I found one of these suckers on a bonkers chalice frag. Dipped and scraped thought I got it all off. Now this dude appeared anyone know what it is? Or if it’s harmful.
If you just have one, then I would get some of your reef epoxy - the kind you mash up to mix ... make yourself a little ball of it .. and get it over the top and encapsulate it. Smash it over it and into the rock.
You can do the same thing with gel super glue if you have some and are good with it. I’m not. So I use reef epoxy.
But you should try to get it covered or out of the tank soon.
I second the super glue.... Glue it's mouth shut then cover the rest in glue. Stick the bottle right in the water. Better to waste 2 bucks then have aiptasia >.<