Pretty much anything that moves that a sunfish will eat, is good. I raised 7 baby bluegill (type of sunfish) to adulthood using whatever I could find or had. If I killed a fly with a fly swatter, I scooped up the dead fly and drop him in with the bluegill. If my guppies had babies and I had no room to keep them, in they went.
I left an old waterfall decoration outside even though the pump went missing. I'd regularly empty mosquito larvae out of it, and feed those to the bluegill. Never had a mosquito indoors - they'd eat all the larvae. I raise mealworms too. My betta fish eat the babies, the bluegill ate the rest.
Variety is good. So as long as they are catching and eating the minnows, they are fine. But don't be afraid to toss other things in now and then.