My Otos eat Cucumber, Zucchini, Wardley's Algae Wafers and Hikari Bottom Feeder wafers. They didn't like algae wafers till I fasted them for a day then they tried it and now they love them.
After that they started eating the Hikari Bottom Feeder wafers that I put in the tank for my Cory Catfish. Sometimes fish wont eat what doesn't look or smell like their usual foods. When they get used to it they may try a bite and either like it or not.
Here are 3 my Otos searching for the Algae wafer I just put in the tank.