Transitioning to frozen was pretty easy for me. Get some large mysis shrimp and just place them on a toothpick or stick and wave it in front of him. If he doesn't eat, don't worry, just give it time. Eventually, he'll get hungry enough to eat. After the first few times of feeding frozen, I could just throw some in and he'd stalk them as if they were alive, but feeding by hand is so much cooler.