I have the fireworms in my tank and never had a problem with them. I do know they will eat any left overs that the fish miss, if you see one you most likely have 100's they can be really really small. I have seen one the size of a hair.
the larger ones can eat more and I have heard that they can eat soft corals but I have never had that happen to me. I just pull them out when I see a large one. You can also get a Coral Bandit shrimp he will eat them, I see my guy run around the tank and pull them out and then chow down.