what to feed arowana

My baby arowana (5 inch) hasn't eaten since I got him last Saturday (4/28). He ate a cricket at the pet store the day I got him and he hasn't eaten since then. I have the water in his aquarium at 78 F. He is in there with a 1.5 inch pacu, 2.5 or 3 inch Oscar, and a 4 or 5 inch clown knife. They...