Ulrey's tetra
Hemigrammus ulreyi
A discreet, refined tetra with a broken black line running along the flank, interrupted by a luminous spot at the caudal peduncle. Less flashy than more famous cousins but with a subtle charm appreciated in well-set-up biotope tanks with dark, tannic water. Breeding considered challenging compared to other tetras — eggs and fry are extremely light-sensitive and must be kept in darkness. Ideal for hobbyists seeking a less common tetra to enrich a South American biotope.
Temperatura da água
22 - 27 °C
Valor de pH
6 - 7.5
Tipo de água
Água doce
Nível do tanque
Meio
Tamanho adulto
4,5 cm
Volume mínimo do tanque
>= 70 L
Grupo mínimo
>= 6
GH
2 - 12 dGH
KH
1 - 6 dKH
TDS
40 - 240 ppm
Condutividade
63 - 375 uS/cm
Descrição da espécie
Geographical Origin and Habitat: Paraguay River basin in South America. Inhabits the lush flooded lagoons of the Pantanal and streams with thick patches of plants and floating water lilies.
Taxonomy and Morphology: Ulrey's Tetra (Hemigrammus ulreyi). Often wrongly labeled and confused with Hyphessobrycon heterorhabdus (Flag tetra). Differs in its stocky profile and the absence of the continuous red line.
Social Behavior: Subtle elegance in a school. Less frantic than an Hasemania, it navigates with measured darts but cannot do without a large group (at least 8 specimens) to move in sync.
Coloration and Sexual Dimorphism: Sober and metallic: semi-transparent body surmounted by a clear triple white-black-yellow horizontal line along the flanks (flag), with a black-spotted dorsal fin bordered with yellow. Slender males; very corpulent females at the waist.
Cuidado, criação e companheiros de tanque
Aquarium Setup: Classic planted tank, shielded lighting and horizontally positioned tree trunks. A carpet of low plants (Eleocharis, Lilaeopsis) gives them a great sense of security.
Diet and Feeding: Microscopic mouths, require freeze-dried crumbs. Micro-predators: they like daphnia, frozen Cyclops and decapsulated lobster eggs, but they regularly pounce on normal basic flakes.
Water Quality: Robust cyprinid that excels at temperatures of around 24-25°C (75-77°F) and forgives beginners in case of small nitrate accumulations, remaining active even if the values are not amateur-pure.
Compatibility and Cohabitation: Fantastic as a schooling fish for Loricariids, Apistogrammas (Borellii) and excellent cohabitation with southern pencilfish (Nannostomus). It is totally defenseless against aggression, never mix with Midas Cichlids or similar.
Aquarium Breeding: Careless egg scatterer in mosses or dense plants in the early morning, with the male ramming the partner's flanks to induce ovarian discharge. They cannibalize the eggs in minutes.
Risks and Diseases: Identity confusion at purchase: make sure you buy true Ulreyi. Sensitive to the classic thermal shocks or fluctuating pH typical of newly set up tanks (new tank syndrome).
Origem e distribuição geográfica
Paraguay River basin in South America. Inhabits the lush flooded lagoons of the Pantanal and streams with thick patches of plants and floating water lilies.
Origem
Extra-Amazônica América do Sul
Perfil de peixe
- Temperamento
- Peaceful
- 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.
- Dieta
- 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.
- Expectativa de vida
- 3-4 years
- Tamanho adulto
- 4.5 cm
- Proporção sexual
- 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.
- Frequência de alimentação
- 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.
- Carga biológica
- Low
- 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.
- Fluxo
- Strong
- 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.
- Risco de salto
- No
- Reprodução
- 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.
- Compatibilidade e companheiros de tanque
- Peaceful
- 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.
- Nível do tanque
- 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.
Modelos e parâmetros científicos
FishBase
Acesso aos dados científicos oficiais da espécie
FishBase v25.04Dados sincronizados em: 15/06/2026
- Nível trófico
- 3,2 ± 0,4 se
- Resiliência
- Alta (menos de 15 meses)
- Unicidade filogenética (PD50)
- 0.5
- Relação bayesiana comprimento-peso
- a = 0.01995, b = 2.97
- VulnerabilidadeVulnerabilidade baixa (10 / 100)
Galeria de imagens
Imagens licenciadas vinculadas à espécie ou, quando marcadas, ao táxon representativo mais próximo.
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