I just coated it with kalkwasser. If it lives I’ll pull the rock an coat it in epoxy or CA.From what I understand aptasia x still has the possibly to allow it to release spores for new babies to grow. What I've done in the past with success is to take a piece of live rock big enough to cover the aptasia then put a good amount of gel gorilla glue on the small rock and press it over it preventing it from releasing spores..
I used Aiptasia x 7 months ago on 1 Aiptasia and no sign ever since. if you have any epoxy you could stick in on there.