There are actually quite a number around here who have experienced some success with paired or multiple aros in the same tank. I had a bonded spawning pair in a 950gal for many years (in truth, they only spawned once while I owned them). I originally bought 5 10-12 inchers and removed the most aggressive ones until I had 2 of slightly different size that kept together. Turned out to be a M/F pair. I got a spawn out of them before moving to a new home. The fish were set up in the same tank but, never spawned again after their relocation.