They can be picky when you change food on them, but most species will eat just about any fresh or frozen shrimp, squid, or snail. Freeze dried krill also work well. I do not recommend fresh water prey.
If the animal does not eat, don't panic. Every day or two, offer a small piece of the same food. Sometimes they won't eat for a couple of weeks, but eventually they will come around.
If you can, feed an occasional snail or hermit to make the animal exercise its raptorial appendages. In some smashers, this can help elimante loss during a molt.
Roy