Mine typically just grab scraps of food floating by, but I do also hand feed them 2-3x a week a small piece of krill or silverside.
Beyond supplemental iodine (for molting) I don't think there is much else they require.
Mine usually grab mysis when I feed the tank, and I usually give a little piece of mysis to both the cleaner and peppermint.
I don't actually add iodine itself, but it is in the trace element solution i use.