notice I'm a newbie here... what I've observed in my tank with bristleworm is that when I've seen them in my sandbed (up against my glass) near my long tentacle anemone, they seem to irritate it. If I see one there and my anemone has been sad, I will remove the worm (carefully, so as not to hurt the anemone or myself!)... within a few days the anemone perks back up. Maybe it's just part of the natural cycle of the anemone, maybe it's related to bristleworm removal. I'm careful to use tweezers with them myself as I've been "stung" by the bristleworms before and it can be irritating. However, I agree with the leave them in and let them eat the nasty stuff, just as long as they don't irritate anyone I paid for!