this by the descriptions sounds like a bristle or fireworm for sure, I had them and had to bleach all my live rock, coral rubble and disinfect all coral it was complete madness, got there...eventually 4 years later, they had actually horrifyingly eaten my chocolate tang, it usually sleep under rock on its side and the worms ate off its mouth it could eat as tangs have specialised mouths and died went to burry it was carring it with fish tongs and the worms started to spew out of its mouth and it was gory as it gets so..... oh! and they all through my crushed sand literally! you would find 5 every inch! and there was a 5incher! anyway took down the whole tank and now looking better than ever! instead of taking the tank down in your case I would try baiting them if it is only a few so I would get netting put a dead prawn and the bristles would get stuck in the netting you can look more on that up on the internet and other tricks good luck ;)
