Not for me. I have a 23" pacu with a 26" silver aro (which have been together for almost 2 years, since the pacu was 2.5" and the aro was 6"). They did fine until the pacu got to about a foot long and started a habit of biting the aro's fins off. It continued to do it almost daily until it was around 20", and then it stopped for a while. Now it just does it maybe once every two weeks, but it is still enough to make me wish I had never bought it in the first place.
Edit: And btw, this is in my 225 gallon aquarium. The minimum recommended tank size for pacu is around 500+ gallons, which I think may be why mine is so aggressive.