I have about a hundred pacu and they eat every vegetable that I throw in plus pellet food, I have caught them on cabbage and cucumbers. If that's not enough they eat the water plants. I would not exactly call them aggressive eaters but they will out eat anything else in your pond if you are feeding pellets. I have not seen them chase other fish away from food they just crowd in and eat. In my experience they get big fast, I planted 3 months ago at 1 3/4" they are now 11-12" at about a pound. A friend has two year olds at 4-5 lbs and I think Don Smith told me his 3 year olds were 12 lbs.

1/4 & 3/4 acre ponds. A thousand miles from no where and there is no place I want to be...
Dwight Yoakam