I feed mine 'pleco kabobs'. I cut up zuchinni, pumpkin (he loves this), squash, and sometimes mushrooms if my wife and I are having them too. The mushrooms I always serve fresh, but the other stuff I cut up and freeze in a big ziploc bag.
Then I take out a piece or two of frozen veggies, and impale them on a metal kabob skewer. I slip a nib of airline tubing over the sharp end so the bug dummy doesn't poke himself while swimming or eating, and drop the kabob in the tank.
The weight of the metal skewer holds it to the bottom, and that way I don't have to blanch the veggies. More nutritious that way. This also makes cleanup a snap. I use an old coathanger to snag the ring end of the skewer and just lift it out of the tank in the morning. Slip off the tubing that covers the sharp end, and slide the rinds off into the garbage can. Soooo easy, and pleco gets to rasp his veggies all night.