They can be feed just about anything, but should be feed a pretty heavy green diet to keep them healthy. Putting a nori sheet in your tank everyday is a good start.
I only feed my tank every 2-3 days. I try to put a piece of nori in daily but prob average 6 days a week. They are very hardy fish. Fed your tank as usual maybe put a piece of nori on a clip before you leave for work. It will find it when the lights come on.