i think that is aptasia next to the gonio/zoa. The jury is out on what both are. Any ideas on killing the aptasia without hurting the neighbor?? I've tried scraping but it's come back.
It takes only one cell for it to grow back. Scraping it will only send it into protect and populate mode. Never did the super glue idea. Probably your best bet or scrape the zoa off and put it on a different frag and get rid of the rock it is on. You DON'T want aiptasia. I had it. Did the scraping first, boiling hot water injection with a syringe in the mouth method, and hit or miss peppermint shrimp method(it was a miss).
In all seriousness though, I would try a peppermint shrimp first and if it doesn't eat it in two-three days I would try to glue over it. My personal favorite method is to smother it with epoxy stick but that one it a bit small and there is not a whole lot of space to work in.
I have done the super glue route and it's worked most of the time. The only time it didn't was if the rock had lots of holes in it. Then it would just pop out of a new hole lol.
Aptasia RX or a Berghia Nudi. Have used both. Find that I have just enough aptasia in my sump to keep my Berghia busy and well fed without an infestation taking hold.