Show clear pictures of before and after pics with the lights on. Also, your picture of the bristleworm is not in focus. IMO, your video is not clear enough to indicate there was even GSP or that the bristleworm was eating the coral. Basically, I don't have enough information to know whether it was the bristleworm or something else that damaged the coral or even if the coral was damaged.
Justkidding: do you have hermit crabs?
It's stupid to try and lump all bristleworms into the same category since there are 10,000+ species (bristleworms are in the class polychaeta). Read this:
http://www.chucksaddiction.com/hitchworms.html