Perhaps hes talkign about the stalk in the middle of the starpolyp.
I think I forget the name now, but their like a feather duster but witha trap door and no fan. They let out a stream of mucus to trap particulate matter and suck it in againa t the end of the day.
If thats the case they are harmless and actually snails. their mucus often gets caught by other corals, but thats fine, they eat what it eats for the most part.