Sorry I took a bit to get back with ya Blout.
This question prompted me to do a little searching to see if there has been further developments in the worm/marine world. Worm are an enigma at best. About 99.9% of them are more beneficial than detrimental. Yet they still provoke responses anywhere from mild surprise, to outright heart failure..
About the best advice I can give is this quote which sums up my experiences and knowledge on the matter...
"most worms are harmless but still opportunistic meaning they won't pass up an easy meal. Typically they are lured out into the open by dead or dying organisms and arrive en masse to consume the necrotic flesh. I've often heard reports from folks who say, "Bristle worms have killed my coral." When in fact, the coral was already dying and the worms were just doing what they do."
I have had your circumstance occur to me on a couple of occasions. It was frightening, but ended up isolated to the one specific coral, leading me to believe that the above was in fact, true. Keep an eye out to see if the worms continue their behavior to other corals or not.
Worms are beneficial, but heavens, not one of us wants to see them an inch thick in our DSB. Overfeeding, or lack of an adequate cleanup crew aids in their reproduction.
Most Wrasses are good at munching on them. There are also a few select crabs and other invertabrates that can help, but without searching for your tank setup, I am cautios on recommending some...ie:Arrow crabs.
GL
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