I take and cut zuccini in half and boil it. Most of the time it still wont float so i have to zip tie it to a old rio power filter mount that i bury under the substrate.
My pleco immediately goes for a few nibbles and within the hour he goes to town hollowing it out.
The first time i fed it to him i cut some slits and put wafer sticking out of the top so he would notice it.
I try to feed then that once a week to suppliment the wafers