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Phoenix Tetra

Hemigrammus filamentosus

Fascinating tetra with unusual shapes; the adult male develops white feathery filamentous extensions ('filamentosus') on the anal fin and a shimmering red/pink coat.

Taxonomy
Class:Actinopteri
Order:Characiformes
Family:Characidae
Genus:Hemigrammus
Species:Hemigrammus filamentosus

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Water Temperature

24 - 28 °C

pH Value

5.5 - 7

Water type

Freshwater

Tank level

Middle

Adult size

4.5 cm

Minimum tank volume

>= 80 L

Minimum group

>= 6

GH

1 - 10 dGH

KH

1 - 6 dKH

TDS

25 - 210 ppm

Conductivity

39 - 328 uS/cm

Species description

Geographical Origin and Habitat: Rare endemism of the Araguaia River basin in Brazil. Inhabits shallow water bodies surrounded by grasslands, flooded oxbows, and small tributaries characterized by dense floating and marginal vegetation.
Taxonomy and Morphology: Phoenix Tetra (Hemigrammus filamentosus). Recently discovered (2011). The distinctive morphological feature, unique in the genus, is the extreme filament-like elongation of the first rays of the anal and dorsal fins.
Social Behavior: Very active, lively, and strongly gregarious. Males engage in frequent exhibitionist displays by extending their long fin filaments to intimidate rivals or court. Must strictly be kept in large schools (10+).
Coloration and Sexual Dimorphism: The name "Phoenix Tetra" derives from the dazzling flame-red color of the dorsal, anal, and caudal fins of dominant males, enhanced by the long white filaments. Females are less colorful, lack long filaments, and are plumper.

Care, breeding and tankmates

Aquarium Setup: Long tank (at least 80 cm / 32 inches for rapid horizontal swimming). The aesthetics of the fish are maximized with dark backgrounds, lateral or dimmed lighting from floating plants, and abundant vegetation (Myriophyllum, Cabomba) on the sides.
Diet and Feeding: Flexible omnivore. Quickly adapts to dry flake or micro-pellet foods. However, the glowing "phoenix" colors will only emerge by regularly offering Daphnia, brine shrimp, and frozen bloodworms.
Water Quality: Not particularly demanding like other rare Characins, but prefers weakly acidic and soft waters. Good water circulation with adequate oxygenation will simulate Amazonian rains.
Compatibility and Cohabitation: Peaceful, but the long filaments of the males are an irresistible target for "fin nipper" fish (e.g. Tiger Barbs). Coexists well with other Tetras, rasboras, and Loricariids, provided they do not nip their fins.
Aquarium Breeding: Males furiously chase females among fine-leaved plants. The tiny, non-adhesive eggs fall to the bottom. The use of a spawning net or synthetic mop and prompt removal of parents are essential.
Risks and Diseases: Deterioration of the delicate fin filaments is the first sign of water stress or overcrowding. Fungal infections can quickly attack injured fin rays.

Geographic Origin and Distribution

Rare endemism of the Araguaia River basin in Brazil. Inhabits shallow water bodies surrounded by grasslands, flooded oxbows, and small tributaries characterized by dense floating and marginal vegetation.

Origin

Extra-Amazon South AmericaEast Asia

Fish profile

Temperament
Semi-aggressive
They are exceptionally peaceful and somewhat shy, requiring a large school of at least six individuals to feel secure. When kept in smaller numbers, they may become stressed, lose their vibrant colors, and hide continuously. A proper schooling environment encourages their natural, confident behaviors and tight grouping dynamics.
Diet
Omnivore
In the wild, they are micro-predators feeding on small insects, worms, and crustaceans. In the aquarium, they readily accept high-quality crushed flakes, micro-pellets, and freeze-dried foods. Supplementing their diet with live or frozen foods like daphnia, baby brine shrimp, and bloodworms will enhance their coloration and vitality.
Sex ratio
School
Keeping a balanced ratio or a slight majority of females is generally recommended to prevent males from constantly harassing a single female. In a large enough school, the sex ratio becomes less critical as aggression is dispersed. A larger group naturally forms a healthy hierarchy, minimizing any stress related to breeding behavior.
Feeding frequency
Twice daily
It is highly recommended to feed them two to three small meals a day rather than one large one. Offering only what they can consume within a couple of minutes ensures minimal food waste and prevents water quality degradation. Frequent, small feedings closely mimic their natural foraging behavior in the wild.
Bioload
These small tetras produce a minimal bioload, making them excellent candidates for smaller or heavily planted aquariums. They do not generate significant amounts of waste compared to larger species, reducing the burden on the filtration system. However, keeping them in large schools will naturally increase the overall waste output, requiring adequate biological filtration.
Flow
Stagnant
They prefer a moderate to low water flow that simulates the slow-moving tributaries and flooded forest regions of their natural habitat. Strong currents can exhaust these small fish and cause them significant stress over time. Providing areas of still water, particularly near dense vegetation, allows them places to rest comfortably.
Reproduction
Oviparous
Breeding these tetras can be challenging as they are egg-scatterers that provide no parental care. They require soft, acidic water and dim lighting to trigger spawning behavior successfully. A separate breeding tank with fine-leaved plants or a spawning mop is necessary, and parents must be removed immediately after laying eggs to prevent predation.
Compatibility & tankmates
This species is incredibly peaceful and thrives in a community setup with other similarly sized, non-aggressive fish. Excellent tank mates include small rasboras, Corydoras catfish, and peaceful dwarf cichlids. They should never be kept with large or aggressive species that might view them as prey or cause them undue stress.
Tank level
Middle
These fish primarily occupy the middle to upper levels of the water column in the aquarium. They are active swimmers that appreciate ample open swimming space combined with areas of dense planting. While they occasionally dart to the surface for food or explore the bottom, they will spend most of their time cruising the midwater.

Window to the official scientific data of the species

Data synced on: 06/15/2026

Scientific Parameters & Models

Trophic level
3.2 ± 0.4 se
Phylogenetic uniqueness (PD50)
0.5
Bayesian Length-Weight
a = 0.01259, b = 3.05
VulnerabilityLow vulnerability (10 / 100)

Image gallery

Licensed images linked to the species or, when marked, to the closest representative taxon.

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Last updated: 06/30/2026