worm ID needed

They are filter feeders and are good for your tank.

 

they CAN reach plague proportions and the mucus net the produce can irritate some corals and in general make a mess.... but they don't really HURT anything, they do feed on suspended particulates like bacteria, fish poop, excess food, and detritus.

In my tank I usually don't see them except when I blast my LR off, then every web gets a thick coat of gunk and you can see how many there are. I have a couple of the larger Caribbean variety that spin out mucus webs that can be 12" long and cover a large area of rock and tank... they're neat to watch and don't seem to bother the mushroom corals they're growing out from under.

I've heard there are a few species of wrasses that will eat them... lunaris I think?