When I went through my Oscar phase, I looked at all my local stores and Petsmart had the best looking ones. I purchased two to grow out in my 210g. They both looked were very active and looked to be healthy fish. As they grew out one was obviously growing out weird and was a bit stunted and had digestive issues and had to be put down. The other grew very fast and looked nice. So my only real advice is the same as everyone else, look for active, healthy fish with nice patterning.