They grow huge, need lots of swimming room, are prone to a group of weird parasites and are not reef safe (grin).
Here is a blurb about them from a book I wrote many years ago:
Scrawled filefish, Aluterus scriptus or Alutera scripta
Reportedly capable of reaching almost four feet in length, (FishBase 2006) the Scrawled filefish is usually found much smaller than that. This species is found throughout the tropical oceans of the world where it feeds on a variety of seagrass, algae and gorgonians. In captivity they adapt to krill and mysids shrimp as well as gelatin diets. Sometimes, these filefish have difficulty getting enough food to keep from becoming emaciated. This may be a situation where the fish is being out competed by tankmates for the food, is suffering from internal parasites, or it may be that the artificial captive diet does not meet the animal’s needs as it should.