A very, very large tank, with an abundance of live food, and few, if any, competators. Certainly no aggressive fish in the tank. Even then, there is the fact that these fish simply seem to never adapt to captivity; the stress of being in a confined glass cube, rather than endless oceans, reefs, and mangrove swamps, may take more of an adjustment than theyre able to make. With so many other interesting fish available, with good track records, I cant ever suggest something like a bat or a sweetlips.
If you Really want a batfish, and have the tank to house it properly (I would say 500g or larger), you may want to consider an Orbic. Not as attractive as the Pinnatus (though pinnatus get pretty drab as they mature), but they are much more likely to settle in to captive life and accept a wide variety of foods. Theyre also much less prone to disease (Ive seen seriously ill/injured individuals make miraculous comebacks).
