If you have one aptasia, better to do overkill imo.
I use a syringe and air tubeing and inject kalk into their hiding place (with flow off.) Wait 5-10 minutes, then vacuum out, watching the line to see if the aptasia comes out.
I was going to suggest tossing the rock if it was small, but what you did should nuke it pretty well. You don't want to pull it off of scrape it off in the tank though, because then you will have tons of aptasia