JoeDizzleMPLS;1533568; said:depending on what types of filter media you have loaded in there, those filters should be sufficient, more is always better. people usually try to turn over 10x their tank volume per hour, but with good quality canisters, you should be fine with 3-4x turnover, especially with young piranhas.
you also need to factor in the water change schedule. if you have a good water change schedule then your filtration wont be quite as crutial. i change out an average of 50% a week on my rhoms tank.