Yellow Tang

Snapshot: Meet the sunshine fish — a dazzling daffodil yellow, radiating luminosity. Its stark white scalpel markings demands attention. This one unfortunately doesn't have its full set of dorsal fins. However, that hasn't hindered its ability to swim.
 
Other tidbits: Can grow up to 20cm or so. Range extends from the Great Barrier Reef, off Australia's Eastern Coast, across much of the Pacific. Yellow by day but watch as night falls, when they transform into a muted, almost grey hue. 
 
Bare bones must know: Live-rock fish-only system, or reef aquarium.