I have my RTG 8" with two peacok Bass 11" /flag tail 8"/ 4 silver dollars 4". They are in a 220g tank. Aro was the last to join the tank and he only goes after silver dollars occassionally. pBass have much more body mass than the aro so far therefore no threat there. Anyway, from what I read from the above posts things have the potential to go bad only when the aro matures more, but even then I guess my pBass would be hitting around 18".
The biggest problem i found with the larger peacocks was that they dont fight back . So even the one that was much larger then then my arowana didnt stand a chance. They also dart away once the aggression starts and normally do just as much if not more damage to themselves hitting decor/sides of the tank then the arowana could do to them.
My Aro also seems to have mastered killing fish, he'll swim along side just behind the fsh, then he goes up and over bites down on spine right the base of the tail as he spins around them almost like "balling" behavior i see when other fish breed, but in this case he seems to be trying to twist the tail right off the other fish.
Although if someone had asked me a few years ago i would have had all these same fish listed as potential tankmates as well l because i had no problems at all for the first couple years. Everything was fine until it wasn't any more.
If it helps for those who still have RTG's playing nice, when mine started killing it happened very quickly, but I had seen some " warning signs" before that.
He a few months earlier had started to show his more dominate side he would swim alone side any large fish in the tank , pressed right up against them and flare, push them down to the substrate. No biting but clearly displays of dominance. it was very entertaining at first watching him and the oscars swim around side by in the little "swimming competitions". Then the arowana discovered how to bite and that was the end of his peaceful dominance over the tank, and once he started killing it went bad fast!
In the future if i saw this swimming along side , and topping of tankmates I would separate the RTG, at the time I didn't expect him to start killing though, after 2 years of peaceful living i didn't see the pushing and topping as the warning sign that he was getting aggressive.