My 5" baby silver does it too, I think they're looking for a way out. Give him some plants at the top to hide in, seal that lid tight and no holes ANYWHERE. Keep a couple desk lamps with amber bulbs clipped on the sides, cheap at walmart- and turn off your main aquarium light, be sure the room isn't brighter than the tank. It can take them up to 3 days normally to eat, presoak a piece of hikari (1/2) and dip it and presoak it for about 5 secs and if he doesn't eat, remove the food.
Paramters are vital in the survival of your aro. Try to heat it up a notch and put some salt in there. (read instructions)
Good Luck
I also used an angelfish as a nanny.
mei