Flag Cichlid (Festivum)
Mesonauta festivus
The Flag Cichlid (Mesonauta festivus), historically known as Festivum, is an elegant South American cichlid with a unique appearance and behavior. It is instantly recognizable by the strong black diagonal band that crosses its yellow/olive-green body, starting from the mouth, cutting through the eye, up to reaching the terminal part of the pointed dorsal fin, making it look like a raised flag. Unlike most large cichlids that station on the bottom, the Festivum is strictly a surface fish, patrolling the high fronds and looking upwards waiting for insects, making it an ideal companion to exploit the upper part of large Amazonian tanks.
Water Temperature
24 - 28 °C
pH Value
6 - 7.5
Water type
Freshwater
Tank level
Surface and middle
Adult size
15 cm
Minimum tank volume
>= 200 L
Minimum group
>= 4
GH
4 - 12 dGH
KH
2 - 6 dKH
TDS
80 - 240 ppm
Conductivity
125 - 375 uS/cm
Species description
Geographical Origin and Habitat: Amazon river basins (Brazil, Bolivia, Paraguay, Peru). Prefers slow-flowing rivers, meanders, and lagoons. Almost always found hidden among floating vegetation, submerged roots and fallen branches (Igapo/Flooded forest biotope).
Taxonomy and Morphology: Festivum Cichlid (Mesonauta festivus). Cichlid with unusual shapes. The body is strongly compressed laterally, but instead of being oval, it tends to be triangular/rhomboidal, with very long and thin pelvic fins (filiform) used as tactile organs.
Social Behavior: Calm and timid. Much less aggressive than most large South American cichlids. Swims keeping a characteristic position with the snout slightly pointing upwards to scan the surface. Forms monogamous pairs that detach from the group only to breed.
Coloration and Sexual Dimorphism: Disruptive coloration. Silvery-gray/yellowish background cut diagonally by a clear black stripe that starts from the eye and reaches the end of the dorsal fin. Dimorphism almost non-existent: old males are only larger and with more pointed fins.
Care, breeding and tankmates
Aquarium Setup: Tall tank (min. 120 cm / 48 inches long and 60 cm / 24 inches high). It is a cichlid that lives "suspended" between vertical branches and floating leaves (e.g. Vallisneria gigantea, Pistia). Intricate woods descending from top to bottom are fundamental to give it security.
Diet and Feeding: Omnivore with a strong insectivorous/vegetarian tendency. In nature it picks insects fallen into the water and tender shoots. Feed with cichlid pellets (vegetable-based), bloodworms, daphnia and blanched vegetables (peas, spinach). Frequent eater of duckweed.
Water Quality: Requires clean waters but tolerates "Blackwater" environments rich in tannins well (add Ketapang leaves or alder cones). Optimal Ph 6.5, low or medium hardness.
Compatibility and Cohabitation: Excellent roommate for Angelfish (with which it often shares the biotope in nature), large Tetras, and loricariids. Not recommended with impetuous cichlids (e.g. Oscars, Green Terrors) that would bully it, or with microscopic fish that would be eaten.
Aquarium Breeding: Open Spawners. They clean broad leaves (Echinodorus), flat stones or even filter pipes. Both parents fiercely protect the eggs (about 200) and the young, fanning them and chasing away intruders.
Risks and Diseases: Pathological shyness and Jumping. In tanks that are too bare or with neurotic companions, the Festivum will darken from stress, refuse food and desperately try to jump out of the tank if frightened (lid mandatory).
Geographic Origin and Distribution
Amazon river basins (Brazil, Bolivia, Paraguay, Peru). Prefers slow-flowing rivers, meanders, and lagoons. Almost always found hidden among floating vegetation, submerged roots and fallen branches (Igapo/Flooded forest biotope).
Origin
Amazon, Orinoco, and GuianasNorth America
Fish profile
- Temperament
- Peaceful
- They are generally peaceful and shy. They can become territorial during spawning. They behave very well in community setups.
- Diet
- Omnivore
- They are naturally omnivorous. They prefer plant matter and small invertebrates. Spirulina flakes and frozen foods are excellent choices.
- Life expectancy
- 5-10 years
- Under proper care, the festive cichlid has a lifespan of 5 to 10 years in captivity. To reach this age, they require stable water parameters, a high-quality diet, and a stress-free environment with peaceful tankmates. Regular water changes and a properly sized aquarium are crucial factors in preventing premature aging and disease.
- Adult size
- 15 cm
- The catalog's scalar value is 15 cm. The FishBase SPECIES table (v25.04 snapshot) source reports a maximum adult measurement of 12.1 cm for this species, recorded as standard length (SL). The taxonomic record consulted is Mesonauta festivus (v25.04); male or unsexed record. These figures are not interchangeable: the first is the profile's editorial reference, whereas the second is a published maximum under a specific measurement convention; differences among sources can reflect sex, population, life stage and measuring method.
- Sex ratio
- Group
- They are best kept in established pairs. Groups require very large aquariums. Sexing juveniles is notably difficult.
- Feeding frequency
- Twice daily
- Feed them once or twice daily. They are careful and deliberate eaters. Ensure fast fish don't outcompete them.
- Bioload
- Medium
- They produce a typical moderate bioload. Efficient filtration easily handles their waste. Regular maintenance keeps the environment pristine.
- Flow
- Strong
- They prefer gentle water flow. Avoid excessively strong currents. Calm surfaces provide an ideal, stress-free environment.
- Jump risk
- Yes
- They pose a low jump risk. A secure lid is always recommended. Startling noises can occasionally trigger jumping.
- Reproduction
- Oviparous
- They are monogamous substrate spawners. They lay eggs on flat broad leaves. Both parents actively guard the fry.
- Compatibility & tankmates
- Aggressive
- They are peaceful community cichlids. Suitable tank mates include tetras and corydoras. Avoid very small fish that fit their mouths.
- Tank level
- Top/Middle
- They occupy the middle and upper levels. They appreciate tall plants for hiding. They often rest near floating vegetation.
Scientific Parameters & Models
FishBase
Window to the official scientific data of the species
Data synced on: 06/15/2026
- Trophic level
- 2.5 ± 0.23 se
- Resilience
- High (less than 15 months)
- Phylogenetic uniqueness (PD50)
- 0.5078
- Bayesian Length-Weight
- a = 0.03311, b = 3.09
- VulnerabilityLow vulnerability (10 / 100)
Image gallery
Licensed images linked to the species or, when marked, to the closest representative taxon.
Related species
Recommendations grouped by close relatives, companion choices, and similar care.
