I have a small bristle worm in my tank. I think its only maybe an inch if that. It is in a hole in a small piece of rubble rock but it never comes completely out of the hole. The rock was in my sump/refugium but I took the rock and put it in my main display tank. I'm hoping to get a better look at it and that it will grow bigger. There is also a very small feather duster on that rock. The neat thing is that it has a bright red feather. All my other feather disters have white feathers.