Don't use an acid, it will mess up your tank's PH.
Joes Juice works OK, but it's not perfect. I have a couple bottles here at the house that I'll probably never use and its quite expensive and a nuissance to use on large outbreaks.
The best method by far, is to use a creme brulee torch, or other small torch. You can find them at any cooking store for about $15.
Just pull your rock out and nuke them with the torch. Then rinse that area over a sink using RODI water to clean up all the dead tissue off the rock. Put the rock back in your tank and you are 100% certain it is dead and won't come back.
Just don't burn your house down doing this, like I almost did. I set the torch on some plastic and the heat actually ignited the plastic and started a small fire.