Over the years it's food has changed as availability has.
At present it gets a variety of food but generally only one or two of the following per week.
smelt, silversides, mackerel, herring, lake trout, tilapia, market shrimp. In the past boiled liver, chicken and other fish.
I keep a shoal of guppies and sometimes swordtails in all my piranha tanks So it might eat some of the flake & pellets fed to the smaller fish.
In this ones tank I also have bristlenose plecos and 4 goldfish (I breed all of the live fish that are in with my piranhas) but no swordtails. The goldfish are seldom eaten and replaced with smaller ones every few months.
I use undergravel filters in all of my piranha tanks.
When it shows signs of not eating I stop feeding.
Sometimes this can go on for 2 weeks to a month. Nzafi has experienced this happening sometimes with his rhom also.
Water changes 35% between 2 to 4 weeks.