my aro doesn't chase food thats to small, in his eyes its not even worth the effort of the strike. so its not impossible. i've been growing my buttikofferi since he was 3" with my 2ft aro. now the butti is around 6-7" and the aro still dont mess with it.
My aro has always been kept with many much smaller fish all the way down to 3". If you feed pellets etc then the aro will not look at the other fish as food.
KNH
As you can see there are many people(including myself) that keep aros with bite size fish. I works alot of the time, but be pepared that there is always the chance of losing a fish.