I'm having the same issue with my new 8 inch silver I got yesterday. It's in a grow out tank (55 gal) with a three inche tiger oscar, 5 inch clown knife, 5 inch pleco, 4 inch pictus catfish, 5 inch African knife, two 5 inch bala sharks, and two 3 inch red belly pacus. Community fish from this tank will go to a different 55 and semi aggressive and aggressive will go to a 200. But could these fish be stressing the aro too?