I just realized I didn't answer all of your questions, I don't believe it's necessary to feed twice per day. And yes, variety is appreciated I believe. I can tell my anemones have a more vigorous feeding response with fresh foods that are regularly varied. The foods you have, shrimp and squid are great, you can add to that small pieces of scallop, oyster, silverside (though some report problems with this, I haven't so far fortunately), krill, and mysis.