You could always try medium cichlid pellets, my butterflies love them. Additionally i have one butterfly that follows my biggest senegal around all day, its actually really funny to watch, so i dont think you will have any trouble with that combination. Just be careful when you are doing waterchanges, you leave the lid off for a couple of minutes to dump the water out of your bucket, and you come back to find all of the butterflies have tried to escape, and you have to revive them (carefully moving them backward and forward in the tank to get water through their gills seems to work nicely).