Mine eat everything I feed the plecos! French-style green beans, sweet potato, carrots, persimmon, avocado, beet greens, radish greens, watermelon, spinach... They go for anything I put in the tank.
(I even tried a small piece of Dorito in a small container that I had a few shrimp in that had gotten sucked out at water change. They ate every last crumb and survived. I got the idea from @VickiK giving one to her oscar a long time ago. I won't do it again -- just wanted to see if they would eat it. )