Feeder Fish

Several large fish, including cichlids and piranhas will eat live fish as part of their diet.
It is generally not necessary to "grow your own". Many fish stores stock offer inexpensive "feeder guppies" or "feeder goldfish" as part of their ordinary stock. For fish like piranhas, a small piece of raw chicken or a strip of fish fillet will work just as well as a live fish. Feeding live fish is not recommended because it will increase the aggresiveness of your fish and led to an increased chance of introducing disease pathogens into the aquarium.