My method for dealing with my Galaxea (it was the size of a toddlers head when I got rid of it and had sweepers over 12" long) was to place a BTA anemone. Those LPS types can 'smell' whats around them, and will reach out in the direction they know another coral is... regardless of flow or anything. So, I give them something nasty to smell, like an anemone that can take it on if needed, and since, no more sweepers.
As for the more 'open brain' style LPS... yeah, I had a trachy that sent out a 'spiderman' web at a rock about 8" away covered with rics... covered it with its 'web', and destroyed the whole rock. Sometimes, they do that.