Many of the captive butterflies will eat a variety of foods commonly available. You can buy packaged frozen clam at a well stocked lfs or purchase fresh whole clams from a grocer. Mysis, pellets, flake, occasional bloodworms, minced scallop, squid and mussel are also good. Many will devour nori so add this to the diet.
Skip the panda and copperband. (Poor captive choices). For a hardy bf, look at Blackback, pearlscale, mertens, pebbled, burgess, kleins.