my aro is in a 45 gal tank right now while I build his new home , 125 gal tank. What tank mates would make this the ultimate or at least a really good looking monster tank worthy of calling it a MONSTER FISH TANK.
Agreed...I would say at least a 240, but bigger if possible.
As for tankmates...some of the common ones are dats, rays, bass, bichirs, gars, other aros (be careful with this one)...stuff like that. I tend to avoid nippy fish, like cichlids (with an exception for Cichla sp.), but you can pretty much have anything that the aro won't see as lunch.