I target feed my anems 1-2 times per week. I have a mix that I run through a food processor that includes silver sides, krill, shrimp, scallops, squid, brine, mysis, plankton, formula 1 and 2, flake, and nori. The tank gets this about 2 times a week.
IME, if you have good flow anems seem to do a decent job of pulling food in on their own during regular tank feedings. I also remember reading that, while they can consume large chunks of food, smaller pieces are easier for them to digest. I never give them a whole silver side, and usually won't give them more than 1/5.