Just gotta throw my experience in with this. I had a complete infestation of aipastia, there was a field in my sand and all over every rock. I figured like you that i could get rid of them with boiling water. So, I poured boiling water over them in a bucket, let that sit for a week almost. THEN i took the rocks out and sat them in a freshwater bucket for almost a week outside. After that I put the rocks on the driveway and let the sun bake them for a few days.
Now after all that it appeared they were gone. But lo and behold about 3 weeks later I had more of them. LOL Not sure how long they can survive.
What I ended up doing and what I DO NOT recommend was to nuke my tank with ammonia. I put in a cup or two of pure Ace ammonia and within 2 days all the aipastias were gone. Since I had them in my filter too this got rid of them as well. Drastic measure I know but it worked. Keep in mind I had no live stock in the tank other than a few snails which I pulled out before the ammonia went in.
180g Reef - 60g Rimless Reef -90G FOWLR- 125g Malawi Cichlids- 40b REEF- 34g Fresh Planted-working on- 20L FOWLR- working on
I have a mix of many different saltwater fish amongst my tanks, but I love my Tangs most of all.