Is the tank narrower than fish is long? My guess it is and that's what can stress fish out. In addition LFS guy stressed the Aro even more. So:
1: you need a bigger tank for your Aro
2: try to put some Stress Coat+ or Prime Stress Guard, turn off the lights or better yet cover the tank fully.
3: Don't change more than 50% of water, you'll stress fish even more.
4: What else do you have in the tank?