Mesonauta guyanae

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Mesonauta guyanae, also known as the Orinoco Flag, is an elegant South American cichlid from the Orinoco basin. Its laterally compressed body and bold dark diagonal stripe create an immediately recognizable profile. This species remains uncommon in the aquarium trade, making it an appealing choice for aquarists looking for something less frequently encountered than popular large cichlids. Like several peaceful cichlids, it displays complex social behavior, especially when paired or spawning. The specimens offered are collected from the wild and should be acclimated carefully after arrival.

General description of the species

Mesonauta guyanae is a medium-sized cichlid with a deep, laterally compressed body and long dorsal and anal fins. It belongs to the genus Mesonauta, a group known for its slender shape, distinctive facial pattern and generally calmer behavior than many cichlids of similar size. In an aquarium, it benefits from a structured environment with open swimming areas and retreats. Its temperament may become territorial when a pair forms or spawning begins, but it is not usually a constantly aggressive fish. Its availability remains relatively limited, and wild specimens may be shy during the first weeks.

Geographical origin and biotope

The species is associated with the Orinoco basin, including the Colombian area given for its origin and neighboring regions of northern South America. It inhabits calm to moderately flowing waters, often bordered by vegetation, submerged branches and roots. The natural environment is generally warm, soft to moderately mineralized and slightly acidic to neutral. In aquaria, stable water around 26 to 29 °C with a slightly acidic to neutral pH is suitable. Filtration should be effective without producing excessive current for this fish from relatively quiet habitats.

Precise location and local name

Mesonauta guyanae is associated with the Colombian sector of the Orinoco basin; the information commonly used in the aquarium trade does not allow one single collection site to be stated here with certainty. The English common name Orinoco Flag refers to its general range and its flag-like body stripe. In the trade, it may also be offered simply under its scientific name, without a standardized French or Spanish local name. To preserve the geographical value of wild specimens, keep any collection information supplied by the collector or importer.

Appearance and physical characteristics

The body of Mesonauta guyanae is silver to olive-brown, with a black diagonal band crossing the head and flank. This marking may become stronger depending on mood, surroundings, social rank and lighting. The fins are relatively well developed and may show subtle yellow, orange or red tones. The tall, compressed body, terminal mouth and extended fins fit the general profile of Mesonauta. Adult size is usually about 15 cm, although individual size can vary with conditions and with the method used to measure the fish.

General diet

In nature, Mesonauta guyanae feeds on small prey, plant material and organisms associated with submerged surfaces. In aquaria, it accepts quality cichlid pellets, suitable flakes and frozen foods such as brine shrimp or mosquito larvae. Regular plant matter, offered as spirulina-based food or blanched vegetables, helps diversify the diet. Meals should be small and moderate to prevent excessive organic waste. Juveniles and wild adults benefit from a gradual dietary transition before being maintained entirely on prepared foods.

Essential data

• Original river name: Orinoco and tributaries of the Orinoco basin
• Local name used: Orinoco Flag
• Origin of the scientific name: Mesonauta is the genus name; guyanae refers broadly to the Guiana geographical region
• Etymology of the full name: Mesonauta can be interpreted approximately as “middle sailor”; guyanae is a Latinized form associated with Guiana
• Common/vernacular names: Orinoco Flag, Orinoco Flag Cichlid
• Family: Cichlidae
• Subfamily: Cichlinae
• Name pronunciation: meh-zoh-NAU-tah - guy-AH-nay
• Discovery: Ingo Schindler, 1998
• Maximum adult size: about 15 cm
• Water temperature and pH: 26 to 29 °C; pH 6.0 to 7.2
• Watercourse appearance and surrounding vegetation: calm or moderately flowing water with branches, roots, leaf litter and riparian vegetation
• Typical tankmates: peaceful small characins, South American dwarf cichlids, peaceful catfish and other similarly sized cichlids
• Temperament and behavior: generally peaceful and social, becoming more territorial as a pair or during spawning
• Water depth: shallow to medium-depth areas near banks and vegetation
• Sexual dimorphism: difficult to distinguish outside breeding; size differences and the genital papilla are the most useful clues
• Bottom structure and flow: sand or fine substrate with plant debris and roots; low to moderate current

In your aquarium

To keep Mesonauta guyanae successfully, provide a spacious, covered aquarium decorated with wood, roots and sturdy plants. Warm, clean and stable water is more important than pursuing extreme values. These fish are collected from the wild, so acclimate them slowly and introduce food progressively. Since the species is not frequently available, avoid impulse purchases and prepare the aquarium before arrival. Maintain peaceful tankmates, watch for pair formation and provide several visual retreats to reduce tension.