What do starfish (sea-stars) eat?
There’s no such thing as a ‘normal’ five-legged Starfish, there are dozens of species with similar characteristics. Many species consume small organisms including invertebrates, others will eat algae and quite a few will consume corals. If you don’t know how to feed or care for it then I would suggest putting it back. Animals are not disposable and you can’t just say that you’ll ‘bleach’ it if it dies, put it back where it belongs.