pacu will eat anything you give them. Best is a mix of cichlid pellets, some algae wafers, and regular things you find at the store....grapes, unsalted nuts, bananas, carrots....almost any veggie and many fruits would be good. you can also feed them thawed, uncooked fish fillets from the freezer like tilapia or whatever is the cheapest.
to sum it up, pacu are garbage cans with gills. they will generally eat almost anything they see, including decorations, heaters, wires etc....