they will only eat food that runs from them, literally. I started with guppies then switched to rosies. A couple times before I had my feeder tank set up, there would be too many rosies for them to eat all at once and the left over rosies would school with the bass and as long as the rosies didn't run from them they wouldn't get eaten.
Now that I have the feeder tank, I only feed them a few at a time and always from my hand so I can get them on something else.