Hello Craig,
from your writing I suppose you do not have a pipe organ coral (as they do not grow encrusting but as colonies) but something like Clavularia viridis or Briareum asbestinum...
Rather difficult to remove when it encrusted a lot.
If you could take the rocks out of your tank you can srutch it away.
Pipe oran coral (Tubipora musica) - if you touch the polyps and they hide there is a red sceleton left:
tubipora musica sceleton
if you touch clavularia viridis the skin is almost flat and purple
and if you touch Briareum asbestinum its again flat and the skin is gray or skin coloured
regards
Markus