I have about 44kg of fiji live rock in my tank - managed to get a really good deal on it from my LFS. Noticed about 4 or 5 worms on (or rather in) it now - I don't think they're bristles, as they're not.. bristly.. enough. They're quite dark in colour, and stay in holes in the rock during the day, and during the dawn/dusk time too. They only come out when the aquarium lights are fully off, so I can't really take a photo (I spotted them when having a quick look with a torch a few days ago). They come out of their holes in the rock, grab things off the rock and then retreat back into the holes again, repeating the process. To me, this seems like good cleaner behavior, and I'm really not concerned about the fact there is worms in the tank. What do you guys think - beneficial? My description was probably too vague for an ID, so I thought I'd post it here rather than in the ID forum. Apologies if it's in the wrong place!