Have you tried hoppers? Just about midway between fuzzy and small. He may have been taking smalls for the breeder, but got stressed in the move. Seems like when they get stressed, they sometimes become intimidated by larger prey. You should be able to work gradually back up to smalls. If he won't take a hopper, just ask for the biggest fuzzy you can get. Then the next time, ask for a small hopper...

Also, it will help if you wait a little longer before offering a larger meal. If you're currently offering food twice a week, then wait a full week before offering a hopper. If you work up gradually, you should be able to get him up to smalls fairly quickly.

Steve