I don't feed my anemones fish food. If I want them to growth I feed them seafood that is for human consumption. Feed them spoiled food will kill them, especially the delicate anemones like Magnifica and Gigantea. Frozen smelly silverside likely kill a lot of anemone and the owner just put the death to whatever cause. Feeding silverside may not kill the anemone most of the time, but why take the chance.
I disagree with Neptunes Cove about feeding anemones. I have 10 hosting anemones in my system, about 500 gal total. I feed 1 and two at a time, not all of them. Now I like my anemone size so I don't spot feed them much anymore.
How many of us use flake food or frozen mysis, Nori in our tank? How many tangs will encounter nori in the wild? How many fish will eat flake food in the wild? We feed our fish substituted of what they eat in the wild. If we do a good job at it, then we have healthy colorful fish, if we don't then our fish is dull in color and unhealthy. Fresh unspoiled silverside is perfect anemone food, many of them eat fish in the wild. I just don't use them because there is too high chance of silverside been spoiled and kill my anemone.
-so I asked him- "how often in the wild do you think a krill or silverside would die and fall into an anemone"???
everyone laughed, he became red and embarrassed...
That poor speaker could not think of a quick answer right on the spot does not mean that Neptunes Cove was right. I am sure 15 mins later, he wished that he could have the moment back and would have the perfect answer to Neptune's question on the spot. Many of us, myself included, who does not have quick wits, often get embarrassed on the spot but it does not mean that we are wrong.
Sorry for the long winded answer but feed him unspoiled seafood every 3rd (or more) days if you want him to growth or divided. Otherwise don't feed him if you are happy with his size.