I keep a 13" vieja fenestatus (agressive as hell) a 12" oscar, and a 15" jag with my aro....
none of them ever bother the aro (24")
ETA: I've had a 12" FH in with it as well.

levi we are lucky mofos that the fish we keep with our aros are not pycho's![]()

My 12" jag constantly harassed the 24" aro, so I got rid of the jag. The only big cichlid I have in there is a 14" red snook.
Guinness