Mucus coming out of their mouths? Feather dusters do excrete a mucus to use for their tubes but I think they excrete it from the length of their bodies. Tubeworms are Polychaetes, of the phylum Coelenterata which means the only have one path to and from the gut ie the mouth (no bum!). Its been a while since I did that biology but I think it's right. I constantly see my tube worm passing pellet-like waste from it's mouth, maybe yours has indgestion!