The Flashlight Fish, Photoblepharon palpebratus, is named for its unique ability to harbor light-emitting bioluminescent bacteria in an organ under its eye emitting a glow when viewed in the dark. This is also known as the One-Fin Flashlight Fish and not to be confused with Anomalops katoptron, the Two-Fin Flashlight Fish, which is found more often in the aquarium trade. The One-Fin Flashlight Fish is quite unique and rare in the aquarium trade. The Flashlight Fish does require a unique aquarium set up. Your tank should be dimly lit, a deep water tank, plenty of live rock and overhangs, and they may be best kept in small groups.