my pair seem to prefer smaller sized food, they ignore the bigger chunks of frozen most of the time and also like ON and NLS pellets.
If your away from home a lot make sure you have an auto feeder, they are a very active fish and like to eat multiple times, I have a mix of ON/NLS pellets in an auto feeder for mid moring and day, and then feed frozen when Im home at night. They seem to do well with that schedule.