keep feeding him what he ate before! don't change up alot.
try the crumpled newspaper trick, crumple up loose balls of newspaper and fill his tub. try this for a couple of weeks , then gradually reduce the paper.
try feeding him at night when it's dark and quiet, keep the same feeding and routine, offer food only once a week.
if feeding f/t, if he doesn't strike right away. it's ok to leave in overnight. throw it away the next morning though.
vaughn