To my eyes they look like what people call tube worms. Generic name covering a lot of worms that create tubes and extend apendages out to feed. Most are harmless filter feeders
+1 looks like a bristle worm. Are the tubes kind of hard? They are just harmless filter feeders. Some people say they take over but I haven’t seen that before...
Well woke up to like 15-20 in the sandbed near one of my rock islands. Not sure if I should remove or let them be. I have a melanurus, but I guess he doesn't go after these guys?