For anyone who is having issues with feeding Butterflyfish, please try clams or cockles. They are the single best thing you can use. I had tons of trouble getting my Butterflys to eat until I learned about feeding clams. Cockles are cheaper if you can find them. This was a life saver and all my fish absolutely love them... They all slowly transitioned to frozen mysis, and then to PE mysis pellets and Seaweed pellets.
When in doubt... clam.