Rookie mistake

[sharuq1]

You could just make the part of the affected LR a little island of its own so that it cannot reach the rest of your rock. (which is what I do, gsp is pretty when contained) You could trade the rock for another unaffacted rock. You could sell the rock. You could try peeling it off carefully. That might have mixed results unless you also kill the leftover bits with a chemical or fw.

Or if you really must kill it you could put kalk paste all over it or super glue, or soak it in fresh water for a bit. That last will kill much of the rock, and a torch would definitely kill most of the rock. If you go with the destructo method, don't put it back in your display until it goes back through the ammonia/trite/trate cycle somewhere else (bucket or tank with sw, heater and a PH)