i have a vieja argentea in a 180. his tankmates are silver dollars, a red oscar, firemouth that holds his own very well, chocolate cichlid and two green sevs. my tank gets along great at the moment... but i know about the aggression of viejas and im keeping an eye on him.
i think the aggression really depends on the fish itself-some are just aggressive, and others just arent.. same as with any other fish, there is always an exception to the rule.
they are fast growers-like an oscar. and they love their veggies. when i sink a rock with veggies tied to it, hes always there with the sevs picking at it. if it ever gets to the point where the other fish cant hold their own with him, sadly he will have to go-which i hope never happens because hes such a beautiful fish.