Fish with a brain can spit out spoiled, bad or food that they don't like. Anemone without brain will swallow anything that have certain chemical on it, they cannot tell if the food is spoiled or not. Spoil food are full of bacterial that will get them sick and kill them.
Bad seafood smell, really bad seafood smell real bad. If the food smell, don't feed it to your anemone. I only feed my anemones what I would eat. If I would not eat it, it does not go to my anemones.
I do feed Mysis to my fish, if the anemone catch it, they can eat it. I also rise my Mysis with tank water before I feed it to the tank.