Uaru (Triangle Cichlid)
Uaru amphiacanthoides
The Uaru amphiacanthoides is one of the most iconic and unusual South American cichlids, celebrated by connoisseurs and often avoided by beginners due to its unconventional appearance and specialized care. It possesses a massive oval body (up to 25-30 cm / 10-12 inches) of a sand or umber brown color, furrowed in the center by a gigantic and unique ink-black wedge-shaped spot, with piercing orange-gold eyes. Considered one of the most 'intelligent' cichlids ever (second only to the Oscar), the Uaru is famous for its melancholy gaze and surprisingly peaceful and shy temperament, combined with a strictly herbivorous biology.
Water Temperature
27 - 30 °C
pH Value
5 - 7
Water type
Freshwater
Tank level
Bottom and middle
Adult size
25 cm
Minimum tank volume
>= 400 L
Minimum group
>= 4
GH
1 - 8 dGH
KH
1 - 4 dKH
TDS
25 - 160 ppm
Conductivity
39 - 250 uS/cm
Species description
Geographical Origin and Habitat: Originating from the colossal Amazon River basin (primarily Brazil and Guyana), it is strictly confined to the sluggish, undisturbed backwaters of the "Clearwater" and highly acidic "Blackwater" tributaries. It thrives exclusively in flooded marginal zones, deeply submerged swamp forests, and silent pools, hovering among dense tangles of submerged tree roots and a deep substrate of rotting wood and tannin-stained leaves.
Taxonomy and Morphology: Less famous but equally majestic to its cousin the Discus, the Uaru (also called the "Triangle Cichlid" or "Poor Man's Discus") is a massive, biologically unique species. Its body resembles a massive, flattened teardrop, heavily compressed laterally (though not a perfect circle like a Discus). It possesses an odd, mysterious eye placed very high on its sloped forehead. Adults are imposing, slow-swimming giants that can easily achieve 25-30 cm (10-12 inches) in length.
Social Behavior: An incredibly peaceful, phlegmatic, and strongly gregarious giant. Unlike the vast majority of massive South American cichlids, the Uaru is surprisingly gentle and tolerant. They are shy, highly intelligent, and retiring animals that vastly prefer retreating into the shadowy labyrinth of sunken roots rather than brawling. They form strong pairs and peaceful small schools; when startled, they huddle tightly together, instinctively shifting their color patterns as a defensive camouflage.
Coloration and Sexual Dimorphism: The Uaru possesses breathtaking ontogenetic color development (meaning it radically changes appearance as it grows). **Juveniles:** Exhibit insane cryptic camouflage, looking exactly like dead, rotting black leaves or heavily mottled with a honeycomb pattern to hide in the mud. **Adults:** The body matures into a matte, dusty dove-gray or pale mustard yellow. It is dominated by three iconic, pitch-black zones: a massive, wedge- or teardrop-shaped black patch covering the entire lower flank, a dark "collar" behind the gills, and a piercing, glowing gold/red eye. **Zero Dimorphism:** Males and females are completely identical physically.
Care, breeding and tankmates
Aquarium Setup: Being massive, easily-spooked giants, they demand colossal aquariums: an absolute minimum of 400-500 liters (100-125 Gallons, 5+ feet long). The aquascape must flawlessly replicate an Amazonian "Blackwater" environment. Use soft sand, and fill the tank with massive, arching bogwood pieces to create dark, impenetrable shadow zones. Lighting must be intensely dim, shielded by heavy floating plants (like Frogbit or Water Lettuce). **Plant Warning:** ANY rooted plant, even tough Anubias or Java Fern, will be ruthlessly shredded, uprooted, and eaten. They are unstoppable underwater lawnmowers.
Diet and Feeding: A macro-omnivore with an incredibly strong (almost exclusive in the wild) inclination toward extreme vegetarianism. Their specialized teeth are built to macerate rotting wood and tough leaves. In the aquarium, they will annihilate any lettuce, zucchini, spinach, or aquatic plants you put in. They MUST be fed heavy rations of high-quality vegetable pellets (Spirulina, Kelp) or blanched vegetables. While they greedily accept bloodworms and insects in captivity, an overly meaty, high-protein diet will ultimately destroy their liver.
Water Quality: Just as fragile and intolerant as wild Discus. The Uaru absolutely cannot tolerate any trace of organic pollution, nitrate spikes, or cold water. They demand brutal South American heat (28°C - 30°C / 82-86°F), which kills many pathogens and keeps their metabolism running. Water MUST be soft (very low GH) and highly acidic (pH 5.5 - 6.5). The heavy tannins released by Catappa leaves or alder cones in the water act as a vital natural medicine for their slime coat and immune system.
Compatibility and Cohabitation: The ultimate, perfect tankmate for large, slow-moving Amazonian fish that love sweltering heat. It shares the tank in perfect harmony with schools of Discus (though Uarus are much faster eaters, so ensure the Discus get food), Altum Angelfish, peaceful Geophagus, or massive schools of deep-bodied Tetras (like Lemon or Bleeding Heart Tetras). NEVER, under any circumstances, house them with violent Central American brawlers (Midas, Flowerhorns, Jack Dempseys) which will mercilessly slaughter these "gentle giants".
Aquarium Breeding: Exceedingly similar to Discus breeding, featuring a mind-blowing biological trait. The bonded pair will obsessively clean a horizontal or slanted piece of smooth wood or slate. After laying hundreds of adhesive eggs, the magic happens when the larvae hatch. The parents will allow the massive cloud of fry to physically attach to their bodies, where the babies furiously graze and feed on a *hyper-nutritious skin mucus* secreted by the parents, exactly like Discus. They are fiercely protective parents, but highly prone to panic-eating the babies if startled by sudden lights.
Risks and Diseases: 1. The Hexamita Demon ("Hole in the Head"): This lethal vulnerability, shared with Discus, flares up immediately if they are forced to live in hard, alkaline tap water or fed cheap, dirty flakes. It creates rotting, purulent craters on their face, accompanied by white stringy feces and agonizing death. 2. Overexposure Terror: A tank with bright, blazing LED lights and a white, bare bottom with no wood will terrify them into a permanent state of shock, suppressing their immune system until they die in a corner. 3. Beefheart blockage: Feeding them mammalian meat guarantees fatal intestinal blockage.
Geographic Origin and Distribution
Originating from the colossal Amazon River basin (primarily Brazil and Guyana), it is strictly confined to the sluggish, undisturbed backwaters of the "Clearwater" and highly acidic "Blackwater" tributaries. It thrives exclusively in flooded marginal zones, deeply submerged swamp forests, and silent pools, hovering among dense tangles of submerged tree roots and a deep substrate of rotting wood and tannin-stained leaves.
Origin
Tropical oceans and reefsAmazon, Orinoco, and Guianas
Fish profile
- Temperament
- Peaceful
- They are quite intelligent, relatively peaceful, and can become very responsive to their owners. While mildly territorial during breeding, they lack the extreme aggression seen in many other large cichlids. They form strong bonds with their mates and exhibit highly social behavior when kept in groups.
- Diet
- Herbivore
- They are largely herbivorous in the wild, favoring aquatic plants, fruits, and soft wood. In the aquarium, they will rapidly consume any live plants, making planted tanks nearly impossible. Their diet should consist of high-quality cichlid pellets, blanched vegetables, and occasional protein treats like bloodworms or shrimp.
- Life expectancy
- 8-15 years
- In captivity under proper care, the Uaru Cichlid (Uaru amphiacanthoides) can live for approximately 8 to 15 years. Reaching this age requires keeping them in large, well-filtered aquariums and feeding them a high-quality, plant-rich diet. Because they are highly sensitive to water quality and organic waste, maintaining low nitrate levels is essential to prevent chronic illnesses such as Hole-in-the-Head disease.
- Adult size
- 25 cm
- The catalog's scalar value is 25 cm. The FishBase SPECIES table (v25.04 snapshot) source reports a maximum adult measurement of 25 cm for this species, recorded as standard length (SL). The taxonomic record consulted is Uaru amphiacanthoides (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
- School
- They are nearly impossible to sex outside of spawning behavior. Purchasing a group of juveniles and allowing them to pair off naturally is the most reliable method for obtaining a breeding pair. Unpaired adults can usually be kept together without severe aggression, provided the tank is sufficiently large.
- Feeding frequency
- Continuous
- Adult Uaru should be fed once or twice a day with large, sinking pellets and vegetable matter. Providing romaine lettuce, zucchini, or cucumber provides excellent enrichment and aids their digestion. Young Uaru require more frequent feedings of higher protein foods to support their rapid growth phase.
- Bioload
- High
- These large, heavy-bodied cichlids produce a massive bioload that requires excellent filtration. As messy eaters and large waste producers, they demand rigorous maintenance routines. Frequent large water changes and powerful canister filters or sumps are essential to keep nitrates in check.
- Flow
- Stagnant
- They originate from the slow-moving blackwater rivers and flooded forests of South America. They prefer a moderate flow that keeps the water clean without creating a raging torrent. Providing areas of calmer water behind large pieces of driftwood allows them to rest comfortably.
- Jump risk
- No
- Reproduction
- Oviparous
- Breeding is notoriously difficult, requiring extremely soft, highly acidic water. They are biparental substrate spawners that display a remarkable breeding adaptation where fry feed on their parents' body mucus. This unique behavior mimics Discus and makes raising the fry without the parents exceedingly difficult.
- Compatibility & tankmates
- Aggressive
- They are generally peaceful for a large cichlid, especially when kept with similarly sized, robust companions. They should be housed with peaceful South American cichlids, large characins, or plecos. They will, however, readily consume any fish small enough to fit into their mouths.
- Tank level
- Middle/Bottom
- They generally inhabit the middle and lower levels of the aquarium. They enjoy picking at driftwood and foraging along the substrate for fallen food. A tall tank with plenty of vertical swimming space accommodates their deep-bodied profile nicely.
Scientific Parameters & Models
FishBase
Window to the official scientific data of the species
Data synced on: 06/15/2026
- Trophic level
- 2.8 ± 0.26 se
- Resilience
- Medium (1.4 - 4.4 years)
- Phylogenetic uniqueness (PD50)
- 0.75
- Bayesian Length-Weight
- a = 0.03467, b = 3.05
- VulnerabilityLow vulnerability (21 / 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.
