My afaros are the largest and most docile fish in the tanks. I've never seen them harrass any other fish.
However, young afaros are extremely intolerant of each other. So much so that juvenile afaros must be separated or they'll kill each other. Once they pass the one foot mark, they seem to calm down and get along.
Do a search on this site with african arowana, af aro, and Heterotis niloticus since this species has been discussed frequently. Here's a start for you:
http://www.monsterfishkeepers.com/forums/showthread.php?p=920162#post920162