that's one possibility. it can also decompose and cause ammonia spike. either way it still has a negative effect. but if it's only 5 flakes, don't worry.
It may or it will rot and cause the Ammonia to become deadly and kill you fish. That's why your not supposed to over feed fish, and also the reason you should have a gravel vacuum and vacuum up every last bit of leftover food that's not eaten.
