Black darter tetra
Poecilocharax weitzmani
A small, fascinating Amazonian freshwater fish known for its dark coloration and distinct darter-like behaviors.
Water Temperature
24 - 28 °C
pH Value
4.5 - 6
Water type
Freshwater
Tank level
Bottom
Adult size
4 cm
Minimum tank volume
60 L
Minimum group
>= 1
GH
0 - 5 dGH
KH
1 - 2 dKH
TDS
10 - 95 ppm
Conductivity
16 - 148 uS/cm
Species description
Geographical Origin and Habitat: This species is native to the Amazon River basin, specifically in the Rio Negro, Rio Solimões, and Rio Orinoco in South America. It typically inhabits slow-moving forest streams known as igarapés, characterized by acidic, soft, and dark blackwater stained with humic substances from decomposing leaf litter and fallen branches.
Taxonomy and Morphology: It belongs to the family Crenuchidae, subfamily Crenuchinae. The body is slender and elongated, designed for quick darter-like movements near the substrate. Adults reach a maximum length of about 4 to 5 centimeters. Adult males possess remarkably developed dorsal and anal fins with elongated filamentous extensions.
Social Behavior: It is a territorial but relatively peaceful species. Males establish and defend small territories on the substrate, particularly around caves or leaf litter. It is best suited for dedicated species-only aquariums or community setups with small, non-aggressive tankmates.
Coloration and Sexual Dimorphism: The coloration is dominated by dark gray to black tones, enhanced by iridescent blue and green highlights along the flanks. Sexual dimorphism is highly pronounced: males are larger with longer, more colorful fins, whereas females are smaller, duller in color, and have much shorter fins.
Care, breeding and tankmates
Aquarium Setup: Requires an aquarium of at least 60 liters with dense vegetation and a dark substrate. The addition of dried leaves, such as Indian almond leaves (Catappa) or oak leaves, is essential to replicate their natural leaf litter habitat. Provide plenty of hiding spots using driftwood, tangled roots, and coconut shells.
Diet and Feeding: Primarily carnivorous, requiring a varied diet rich in small live or frozen foods. Regularly feed bloodworms, brine shrimp, daphnia, and artemia nauplii. They are often reluctant to accept dry flakes or pellets, which should only be used as a minor supplement rather than a staple diet.
Water Quality: As a blackwater species, it demands extremely stable parameters: water temperature between 22 and 28 degrees Celsius, highly acidic pH (ranging from 4.5 to 6.5), and very soft water (GH below 5, and KH close to zero). Peat filtration is highly recommended to maintain these conditions.
Compatibility and Cohabitation: Do not house with large, fast-moving, or aggressive tankmates that could easily stress or outcompete this shy fish. Ideal companions include small, peaceful characins like neon tetras, cardinal tetras, pencilfish (Nannostomus species), or small corydoras catfish.
Aquarium Breeding: Spawning occurs in small caves or under leaves. The male coaxes the female into the chosen site, and after egg-laying, the male guards the clutch until hatching, which takes 36 to 48 hours. The tiny fry must be fed infusoria initially, followed by newly hatched brine shrimp nauplii.
Risks and Diseases: Highly sensitive to sudden fluctuations in water chemistry and the accumulation of nitrogenous waste. They are prone to fungal and bacterial infections if kept in alkaline or hard water. A thorough quarantine period is critical before introducing them to an established setup.
Geographic Origin and Distribution
This species is native to the Amazon River basin, specifically in the Rio Negro, Rio Solimões, and Rio Orinoco in South America. It typically inhabits slow-moving forest streams known as igarapés, characterized by acidic, soft, and dark blackwater stained with humic substances from decomposing leaf litter and fallen branches.
Origin
Selective breeding and cultivarsAmazon, Orinoco, and GuianasNorth AmericaEast Asia
Fish profile
- Temperament
- Semi-aggressive
- They are peaceful, rather shy, and deliberate in their movements. They lack the boisterous energy of many common community fish, preferring to observe from the shadows. Males will occasionally display to each other, flaring their fins in beautiful, harmless sparring matches. They require a serene environment to feel comfortable enough to emerge from hiding. When kept in appropriate conditions, their subtle and elegant temperament is highly rewarding.
- Diet
- Omnivore
- They are micro-predators by nature and can be somewhat picky eaters in the aquarium. Their diet should consist heavily of small live or frozen foods, such as daphnia, baby brine shrimp, and microworms. Many individuals may entirely refuse dry flake or pellet foods, requiring specialized care. Offering a varied diet of tiny invertebrates will maintain their health and stunning iridescent colors. Ensuring they get enough food when kept with other species requires close observation.
- Life expectancy
- 3-5 years
- The Black Darter Tetra has an average lifespan of 3 to 5 years when kept under optimal care. To reach this longevity, it is crucial to ensure extremely stable, acidic water parameters free from nitrogenous compound accumulations. Being a highly sensitive blackwater fish, regular and extremely gentle water changes are fundamental to avoid osmotic stress. A varied, high-quality diet rich in live foods directly influences their general health and lifespan.
- Adult size
- 4 cm
- The catalog's scalar value is 4 cm. The FishBase SPECIES table (v25.04 snapshot) source reports a maximum adult measurement of 4 cm for this species, recorded as total length (TL). The taxonomic record consulted is Poecilocharax weitzmani (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 can be kept in mixed groups, with a ratio leaning slightly towards more females being optimal. Males can be territorial with one another, especially when establishing small breeding territories. Providing plenty of hiding spots and visual barriers reduces aggression between rival males. Keeping them in a small group of at least six individuals helps them feel secure. A well-balanced group allows fascinating natural behaviors to emerge.
- Feeding frequency
- Twice daily
- Feeding them once or twice daily with appropriately sized micro-foods is ideal. Due to their small stomachs, small but relatively frequent meals mimic their natural foraging. Care must be taken not to overfeed, as uneaten live or frozen foods can quickly spoil the water. Target feeding with a pipette might be necessary if they are shy or outcompeted. Consistent, high-quality feeding is vital for their long-term survival.
- Bioload
- They have a very small bioload, matching their diminutive size. This makes them ideal candidates for nano aquariums or heavily planted setups. However, they require pristine water conditions, so regular maintenance is still imperative. Their low waste production is easily handled by standard biological filtration. Ensuring low nitrate levels is essential for their delicate constitution.
- Flow
- Stagnant
- They strongly prefer slow-moving water, akin to their natural blackwater habitats. Strong filtration or heavy currents will quickly exhaust them and cause stress. A gentle sponge filter is typically the best choice for this species. Providing areas of completely still water among dense vegetation allows them to hover comfortably. Their delicate fins and small size make a low-flow environment an absolute necessity.
- Reproduction
- Oviparous
- Breeding them in captivity is a significant challenge and requires dedicated setups. They are cave spawners, usually laying eggs on the ceiling of a small crevice or leaf litter. Extremely soft, acidic water (blackwater conditions) is crucial to induce spawning and ensure egg viability. The male often guards the eggs until they hatch, which can take several days. Raising the tiny fry requires highly specialized microscopic live foods like infusoria.
- Compatibility & tankmates
- They are a very peaceful but somewhat shy micro-predator. They should only be kept with similarly sized, docile species, such as small rasboras or dwarf corydoras. Aggressive or fast-swimming fish will easily outcompete them for food and cause them significant stress. Keeping them in a species-only tank or with very carefully selected companions is often the best choice. A calm environment ensures they exhibit their best behavior and natural colors.
- Tank level
- Bottom
- They primarily inhabit the middle to lower levels of the aquarium. They are often found hovering near the substrate, sheltering among botanicals, leaf litter, or plant roots. They rarely venture to the upper levels unless chasing live food. Creating a complex bottom layout with driftwood and leaves suits their natural positioning. Their cryptic nature makes them a fascinating focal point in the lower strata of the tank.
Scientific Parameters & Models
FishBase
Window to the official scientific data of the species
Data synced on: 06/15/2026
- Trophic level
- 3.3 ± 0.4 se
- Phylogenetic uniqueness (PD50)
- 0.75
- Bayesian Length-Weight
- a = 0.01175, b = 3.08
- 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.
