Hi Mark,
I think soaking the rock for an hour or so in chlorox will kill everything. As you know bleach is an all purpose killer. It will oxidize any organics to a point where they just disappear. For example , I drop used frag plugs ,etc in a 50 /50 mix of bleach (chlolrox)and water to clean them up for reuse .There is nothing but clean rocks ,coral skeleton ,etc after an hour or two..
Using a good dose of dechlorinator after such treatment would be very prudent or a soaking in water followed by several days of drying until there is no bleach odor.
I think if the acid treatment is used after the bleach it will neutralize any remaining oxidants.
Aiptasia are sturdy and survive shipping and harsh conditions better than most organisms. . To erradicate them , you probably have to kill most everything else around them unless you can put them in with a relaible predator for a period of time.A racoon butterfly will gobble them up,ime, and lots of corals too but works well for infested rock in a dedicated tank.
I gave up on peppermints after observing them picking on acans and zoanthus.
Consistent and repetative applications of kalk paste on them and into the hole holding their foot will get them eventually without damaging othr tank inhabitants but it's a tedious process and must be done just a little at a time or too much calcium hydroxide will get into the tank water. Fortunately ,at this point I only get a few here and ther from time to time so a weekly hunt deals with it.
An acid bath will kill them as well as a base but the acid will dissolve some ofthe rock . It won't clean up the organics though like bleach will.
Haven't tried a blowtorch but many do that. Not sure you can get all of them at once like a destroy every thing bleach bath.