Cleidopus gloriamaris.
Eight to nine inches long and will eat anything that fits in its mouth.
A good fish for a peaceful, low-light FOWLR...preferably with a sizable cave for it and no small fish or inverts. They're not the most hardy of fish; seem to have some collection problems. Once established and eating, they seemed to do well, but I lost more than a few in the first few days after arrival. I've never kept them long-term, just in the retail environment.
Think of them like a squirrelfish. Nocturnal predators. They wouldn't bother coral, but not a lot of people want reefs without small fish or inverts!