at first they usually only eat live foods, then you when you get them eating and they get comfortable you can usually ween them into frozen silversides and what not. at least this was the case with mine.
I have a fuzzy dwarf. I cant believe I forgot to mention that in my profile. They are very hardy (mine is anyway) never had to feed it live fish. I feed it silversides and shrimp from the grocer even sponges sometimes. What I do is feed the other fish at one end and use a pointed stick to feed the lion. Just put the food on the end and he will come after it. I was forced to feed him that way cuz my puffers are pigs and eat all the food
thats gonna be an awesome pair to watch.. I LOVE panther groupers and lions,,, the groupers just keep getting cooler as they get bigger and atleast he'll be smart enough not to try to eat the lion when he is big enough too