Uaru

The uaru, sometimes called the triangle cichlid, is a large, deep-bodied cichlid native to blackwater and clearwater tributaries of the Amazon and Orinoco basins in South America. It is one of relatively few cichlids that undergoes a dramatic ontogenetic color change, shifting from a bold black-and-white striped juvenile pattern to a mottled chocolate-brown adult coloration. The species is also notable for a rare form of parental care in which adults produce a nutrient-rich body slime that fry feed on directly from the parents' flanks, a behavior shared with only a small number of other cichlid species worldwide.

• Deep, rounded, almost disc-like body shape, adults reaching 20-25 cm
• Juveniles: bold black-and-white striped or blotched pattern
• Adults: mottled chocolate-brown body with darker irregular blotches and a paler outer margin
• Small, downturned mouth suited to grazing and picking food
• Tall, rounded dorsal and anal fins echoing the body's disc shape

The striking transformation from striped juvenile to mottled brown adult is a useful identification cue when comparing fish of different ages; the deep rounded body distinguishes adults from more elongated cichlids.

Uaru inhabit blackwater and clearwater tributaries of the Amazon and Orinoco river basins in South America, favoring quieter stretches with submerged wood, leaf litter, and overhanging vegetation. These waters are typically warm (around 26-30°C), soft, and often acidic to neutral in pH, especially in blackwater habitats stained dark by decaying plant tannins. The species tends to stay near cover and structure rather than open water, reflecting its relatively shy, schooling nature as juveniles that becomes more solitary or paired in adulthood.

Uaru are omnivorous grazers, feeding on algae, plant material, fruit, and small invertebrates in the wild. Juveniles often form loose schools for protection, while adults tend to pair off for breeding. A particularly notable behavior is contact brooding combined with slime-feeding: breeding pairs guard their eggs and, after hatching, the fry feed directly on a nutrient-rich mucus secreted from the parents' skin, a specialized form of biparental care seen in very few cichlid species. Both parents actively defend the brood and continue guiding and protecting fry for an extended period after hatching.