Neochromis omnicaeruleus

Neochromis omnicaeruleus is a Victorian haplochromine celebrated both for the brilliant all-blue colouration of adult males and the extraordinary polychromatic colour polymorphism of females, which can be blue, orange, or mottled black-and-orange. This female colour polymorphism is one of the most studied examples of frequency-dependent sexual selection in cichlid fish and has made N. omnicaeruleus a subject of significant scientific interest.

In the aquarium, the species is an algae scraper that requires abundant rocky surfaces and a primarily herbivorous diet based on spirulina-rich foods. Males are aggressive toward other males and should be provided with well-defined rocky territories separated by visual barriers.

Keeping a group that includes all three female colour morphs creates a visually dynamic aquarium colony and allows observation of the natural mate-choice dynamics for which this species is scientifically renowned.