I have the opposite experience with my rams and they will eat absolutely everything I give them. They're also one of the first fish to swim to the top for food. Sometimes I'm afraid they'll explode with how much they stuff themselves.. I have them in almost all my tanks and they're the first to swim to the glass for food. Flakes, frozen food, repashy, live worms, pellets, even blanched zucchini will have bites taken out of it. They're fearless and the one I keep with my puffers will even run off with whole earthworms, stealing them from my puffer, even though she can't eat it.
Edit: Reading the other responses, I feel like my rams are very broken or just weirdos. No sane fish would challenge puffers for food after all.