It's true that people prefer not feeding live food, and there are many reasons why. If its the risk of your fish dying or getting sick due to feeders, then I believe your making a mistake not feeding them feeders. I think the main reason why people don't feed their piranhas live feeders is not to build their aggresiion, which in turn turns to body flaws, and also lack of coloring on the fishes. On the other hand live feeders help these fish grow faster than dried food and it stimulates their mind. In the end it depednds what your goal is for these rbp's, if you want to beautify them or breed them, then by all measn stick to dried food 100% of the way. If you wnat something a little bit mroe interactive, and are just a regular hobbyists than throw some live fish in there once in a while, as long as their clean(disease/sickness free).