Thanks now off to read up to see if it's good or bad..
Most are harmless scavengers, although I have seen testimonies of some eating corals. That may be a specific species that does that or it might be them eating a dying coral. I've never had the problem with them, though.
It is a violation of federal law to use this product in a manner inconsistent with its labelling.
There are ways to get rid of them like getting a harlequin shrimp, BUT you may need to rehome it after there are no more sea stars, unless you want to spend $6~$10 every two weeks or so to feed the shrimp, as the shrimp only eats sea stars and rarely urchins.