[untamed]

Originally Posted by ScubaSteve

+1 on trimming it if it looks like it's about to go off. Lots of SPS can just go POOF! like someone lighting a fuse once tissue recession starts. Watch it and if it looks to be stable, leave it and hope it will recover. Otherwise, trim the bugger. I'd still recommend breaking off the dead area to encourage the growth of a new axial corallite and branch. Make sure you keep the cut area clean of algae so it can grow back.

I made the mistake a while back of not fragging a colony when it started to receded. Not only did I end up losing 3/4 the colony by the time I finally did frag it to save the living pieces, it also triggered recession in neighbouring colonies. As soon and I got rid of the dying parts in the big colony everything else in the tank was happy and healthy again.

I think this is excellent advice and is identical to experiences that I have had. I also would support the suggestion of "snapping" the dead end off, rather than "cutting/trimming". Sometimes the "snap" doesn't happen where you would like, but a snapped end regrows a new growth tip, while a trimmed end doesn't do it as quickly...and sometimes never.