Only sure way is to never secure one to your main structure unfortunately. I had to hammer and chisel mine out before! Digitatas too. It's the pulsing Xenia of SPS.
Or if you don't have any other Montipora you could get some nudibranchs
Yeah, too late. this is one lesson i wished i learn as a newbie. Its like landscaping, you have to plan ahead. Corals are hard to kill and its not easy to rescape with mature colony. My digitata are not prolific, but the encrusting ones are. Other species i wished i know better is Yuma (or any mushroom ) , rbta , zoas, and the worst of the lot is Pocillopora. I hate poci. those "things" pop up everywhere, in places where i cannot get to. its like aptasia. You can;t kill it. Anyone want rainbow pocillopora, let me know anytime.
If i were to do a restart or a new tank, i'll get only sps stick. Maybe the next lifetime.