Cichla monoculus

Cichla monoculus, the monoculus or flathead peacock bass, is one of the most widespread Cichla species across the Amazon basin and has been extensively introduced beyond its native range due to its value as a sport fish. It displays a golden-olive body with a series of bold dark lateral blotches, clear vertical barring, and the characteristic caudal ocellus shared by all Cichla species.

This species is slightly more tolerant of a broader water chemistry range than some of its relatives, which partially explains its wide natural distribution. In the aquarium, C. monoculus grows rapidly and will reach impressive sizes, becoming increasingly territorial and predatory as it matures.

Like all peacock bass, this fish demands enormous, purpose-built housing and is strictly for experienced large predator keepers. The species is banned for release in many countries due to its devastating ecological impact as an introduced predator — responsible aquarium ownership is essential.

Water: Temperature 24–28°C, pH 5.5–7.5, GH 2–15, KH 1–8; tolerates a broad range but pristine water quality mandatory due to size and feeding. Tank: 800 L minimum for a single adult; very powerful filtration; minimal decor to prevent injury and allow maintenance access. Feeding: Large frozen or fresh fish, prawns, squid, large cichlid sticks; feed 2–3 times per week in adults. Breeding: Rarely bred in captivity; requires enormous space; pair bond formation in large tanks. Compatibility: Species-only tank; will consume any fish, invertebrate, or small object within reach.