Blue Devil

About

The blue damselfish (Chrysiptera cyanea) is one of the most recognizable fish in the saltwater hobby, wrapped in an intense, almost electric blue that holds up even under modest aquarium lighting. Males often display a yellow-orange tail, which makes telling the sexes apart reasonably straightforward once you know what to look for. In the wild, this species is found across a broad sweep of the Indo-West Pacific, living in sheltered lagoons and reef flats where it picks at algae, copepods, and the occasional drifting tunicate. They're daytime fish that naturally organize themselves into small groups centered around a single male and several females or juveniles. Males take their parental duties seriously, guarding and fanning the demersal eggs until they hatch. In the aquarium, the blue damselfish has a reputation that's half admirable and half cautionary tale. It's genuinely hardy and a forgiving choice for newer marine keepers, but its territorial streak is no joke, especially toward its own kind or similarly sized tankmates. Giving it plenty of rockwork and hiding spots goes a long way toward keeping the aggression manageable. One charming quirk: it tends to bob in and out of its favorite cave entrance repeatedly before committing to open water, which never really gets old to watch.