Sounds like the rock is in pretty bad shape with more pest than just aptasia. So nuke the rock for a few minutes as described earlier.
If you have algae on the rock as well, don't leave it in longer trying to get it to dissolve as you will end up dissolving too much of your rock in the meantime. If after a few minutes is has stopped foaming, rinse in tap water then follow up with a 24 hour soak in bleach to remove the remaining algae. Rinse in tap and let it dry out in the sun for a few days.
Thanks for the added info. That's what the plan is. It's been my fowlr tank. I also have my 95 reef and 20l frag. Was just too many tanks with working 60 hours a week, building a new race car, and moms health. Setting up a new frag tank in place of my existing frag tank and the 55.
