Typically it can be peeled away. It tends to grow in a sheet and if you can loosen one corner, you can peel a bunch of it off. I've done this a few times and there are always bits behind that can be eliminated with kalk paste. I use 10 mL of kalk paste every time I do a water change to combat some invasive polyps. Turn off the pumps, apply kalk paste, wait 5 minutes and then suck up the majority of the paste while you proceed with the water change. Just be careful that it doesn't slide down or drip on anything below the area where you are applying the past.
Now that I think about it, getting a decent sheet to pull up is kind of difficult on some kinds of rock where it can grow really strong. I would still try to do that and finish up with the kalk paste.