I would try to get him in a bigger tank. Aro's need very clean water and air. He'll grow faster in a bigger tank. Do you know how to test your water parameters? You can take your water to your fish store to have it checked, or pickup a master freshwater chem test kit for under $40 and do it yourself, (it's easy, you must be very accurate)
The fishy poo changes good water into water with bad bacteria and the water becomes harmful to the fish.
Fish also grow a size related to their tank, to a point. I like starting babies on good pellets, after he's big enough, baby crickets are geat for them.
Aro's tend to be scared of the dark, I'd leave a little night lite on the tank at night, use an airstone for added o2, toss in a floating plant and he'll have a place to hide and feel safer. Best of luck!!!