You can use inexpensive dithers like bala sharks, mahseers, anything that mainly swims in the middle of the tank that wont fit in his mouth. Hang in there, patience with him will be rewarding enough when he finally associates you with food. 
wait so he hasnt eaten now in 3 weeks? And he was eating good before?
Sorry to hear. I have my lights set up so the sides of my tank are dimmer than the middle. My tank is dim in general but I have noticed that my lil 6" aro spends a lot of time in the dimmer areas. He is in a SA com tank. Maybe try soaking his pellets in shrimp or fish water. What I mean by that is when you buy market shrimp try collecting the goo the shrimp leave behind the same goes for if you buy tilapia. That is the method I use to get any of my fish on what I want them to eat.