Encyclopedia / Killifish / Black-fin pearl killifish

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Variations

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Black-fin pearl killifish

Argolebias nigripinnis · Austrolebias nigripinnis, Nigripinnis, Black-finned pearl, Pearl killi, Black-fin pearl

Males are aggressive with each other; keep one male with 2-3 females in a cool tank.

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5 cmAdult size ✓

16–22 °CTemperature ✓

5.5–6.7pH ✓

20 LSmallest tank ✓

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Tank mates

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Not recommended

Black-fin pearl killifish needs cool water and makes a lot of waste, while Cardinal tetra is tropical.
They need different temperatures (16–22 °C vs 23–29 °C). No setting suits both.

Not recommended

Black-fin pearl killifish needs cool water and makes a lot of waste, while Serpae tetra is tropical.
Only a narrow temperature range suits both: exactly 22 °C.

Not recommended

Black-fin pearl killifish needs cool water and makes a lot of waste, while X-ray tetra is tropical.
They need different temperatures (16–22 °C vs 24–28 °C). No setting suits both.

With conditions

Only a narrow temperature range suits both: 21–22 °C.

With conditions

Only a narrow pH range suits both: 6.5–6.7.

Compatible

77 species in our list are a good match.

Facts checked against sources on 16 Oct 2026. ✓ means a source backs it; ? means no reliable source yet. See sources

Care and water

Hardness ✓1–8 dGH

Group size ✓3 or more

Temperament ✓Semi-aggressive

Swims at ✓Bottom

Care level ✓Hard

Diet Carnivore

Lifespan ✓up to 1 years

Size in shops 3–5 cm

Growth Fast

Behavior

Males are aggressive with each other; keep one male with 2-3 females in a cool tank.

cool

Food

Live and frozen foods such as bloodworms, daphnia and brine shrimp.

Tap a food to see what it is.

Male or female

Males are blue-black with many iridescent blue-white spots and dark fins; females are paler yellow-grey to light brown with irregular dark brown spots on the body. A beaten male can turn very pale but never shows the female spots.

Health

Common problems. Tap one to see the signs. This is a guide, not a diagnosis.

Breeding

Annual egg-burier (peat spawner) · Hard

An annual killifish: the pair dives into peat or mud to lay eggs. The eggs rest in damp peat in diapause, a pause in development that lets them survive the dry season, and hatch when water is added; without a dry period breeding fails.

Pairing

One male with 2-3 females.

Setup

20 L tank with a bowl of peat and cool, soft water.

What starts it

Cool water and live food.

Eggs

Eggs are stored in damp peat for about 2-4 months before wetting (sometimes much longer); in nature they can survive dried soil for up to about 3 years.

Raising the fry

Baby brine shrimp from day one.

Common mistakes

Warm water
Not enough dry storage
Hard water

Full breeding guide, day-by-day plan and simulator →

Where it lives in the wild

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Native range (rough area)Centre of the rangePlaces on the World Map

RegionSouthern South America – Argentina, Uruguay & southern Brazil

Rivers and lakesParaná and Uruguay river basins

HabitatSeasonal pools on grassland that dry every summer

Native rangeAbout 500 km across

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The story of the black-fin pearl killifish

A classic cool-water annual killifish from the Paraná and Uruguay basins, first imported in 1908. In the wild it lives only weeks to months in seasonal pools; its eggs survive the dry season buried in mud. Recently moved from Austrolebias to the genus Argolebias.

Charles Tate Regan described this annual killifish in 1912. Its dark males sprinkled with pearly spots made it a classic of the killifish hobby.

First described by C. Tate Regan in 1912. Named for 'Nigripinnis' means black-finned.

Its eggs survive the dry season buried in mud.
Males are dark with pearly blue-white spots.
It prefers cooler water than most tropical aquarium fish.

Sources

17 facts checked with sources

Scientific namecorrected
RENAMED. Legacy 'Austrolebias nigripinnis' was the accepted name from Costa 1998 until 2023; Alonso et al. 2023 moved it to Argolebias, followed by Koerber et al. 2023-2024 and now Catalog of Fishes and FishBase. Older trade name Cynolebias nigripinnis (Regan 1912). Still widely sold as Austrolebias nigripinnis.
Eschmeyer's Catalog of Fishes: species in genus Argolebias · FishBase: Argolebias nigripinnis (Blackfin pearlfish) summary
Familycorrected
Legacy had no family; value is new.
FishBase: Argolebias nigripinnis (Blackfin pearlfish) summary · Eschmeyer's Catalog of Fishes: species in genus Argolebias
Size
size-pick: no Seriously Fish profile. Aquarium figures are 4.5-5 cm (importer, hobby reference) and FishBase common length 4.5 cm TL; FishBase's 7.0 cm TL maximum (Huber's checklist) is far above every keeper figure and is the same number FishBase gives for the larger A. bellottii, so legacy 5 cm is kept.
TropicalFreshwaterFish.com: Dwarf Argentine Pearl / Cynolebias nigripinnis (hobby care reference) · Aquarium Glaser (F. Schäfer): Austrolebias nigripinnis (importer profile) · FishBase: Argolebias nigripinnis (Blackfin pearlfish) summary
Temperaturecorrected
No Seriously Fish profile. Hobby reference 16-22 °C, FishBase 18-22 °C; keep below 25 °C. Legacy 14-24 °C: cooler is tolerated (wild water can drop to about 5 °C per killi.co.uk), but the upper end is too warm for long life. Most hobby breeders spawn it at 20-23 °C (killi.co.uk, 86% of 9 reports).
TropicalFreshwaterFish.com: Dwarf Argentine Pearl / Cynolebias nigripinnis (hobby care reference) · FishBase: Argolebias nigripinnis (Blackfin pearlfish) summary · killi.co.uk species profile: Austrolebias nigripinnis (hobby killifish reference) · Aquarium Glaser (F. Schäfer): Austrolebias nigripinnis (importer profile)
pHcorrected
Hobby care reference 5.5-6.7; FishBase 6.0-7.0. Both below legacy 7.5 upper bound. Hobby breeding reports show it also breeds in neutral water (killi.co.uk).
TropicalFreshwaterFish.com: Dwarf Argentine Pearl / Cynolebias nigripinnis (hobby care reference) · FishBase: Argolebias nigripinnis (Blackfin pearlfish) summary
Hardnesscorrected
Legacy had no hardness; value is new (hobby reference 1-8 dH; FishBase 5-12).
TropicalFreshwaterFish.com: Dwarf Argentine Pearl / Cynolebias nigripinnis (hobby care reference) · FishBase: Argolebias nigripinnis (Blackfin pearlfish) summary
Smallest tankcorrected
40 cm tank, 20 L for one male and one or more females (hobby reference). Legacy 40 L is generous; more fish need a larger tank.
TropicalFreshwaterFish.com: Dwarf Argentine Pearl / Cynolebias nigripinnis (hobby care reference)
Group size
One male with one or more females; legacy trio (1 male, 2-3 females) fits. Never two males in a small tank.
TropicalFreshwaterFish.com: Dwarf Argentine Pearl / Cynolebias nigripinnis (hobby care reference)
Lifespancorrected
Annual killifish: in the wild adults live only a few weeks to months (importer: 'lives in nature only a few weeks'); up to about 1 year in a cool aquarium. Legacy 1-2 years is too long.
FishBase: Argolebias nigripinnis (Blackfin pearlfish) summary · Aquarium Glaser (F. Schäfer): Austrolebias nigripinnis (importer profile)
Temperament
Aggression is mainly male-to-male and toward females; the hobby reference suggests small catfish or small upper-level schooling fish as possible companions. Legacy 's' kept; a species tank is best.
TropicalFreshwaterFish.com: Dwarf Argentine Pearl / Cynolebias nigripinnis (hobby care reference) · Aquarium Glaser (F. Schäfer): Austrolebias nigripinnis (importer profile)
Swimming levelcorrected
Legacy 'middle'; it lives and spawns near and in the soft bottom (FishBase lists 'pelagic', which conflicts).
TropicalFreshwaterFish.com: Dwarf Argentine Pearl / Cynolebias nigripinnis (hobby care reference) · Aquarium Glaser (F. Schäfer): Austrolebias nigripinnis (importer profile)
Care level
Legacy 3 (hard) kept: sensitive, cool water, egg drying needed. FishBase (Huber 1996) says 'Is easy to maintain in the aquarium', which conflicts.
TropicalFreshwaterFish.com: Dwarf Argentine Pearl / Cynolebias nigripinnis (hobby care reference) · Aquarium Glaser (F. Schäfer): Austrolebias nigripinnis (importer profile)
Where it livescorrected
Legacy said Argentina only. IUCN: Near Threatened (FishBase, assessed 2021).
Eschmeyer's Catalog of Fishes: species in genus Argolebias · FishBase: Argolebias nigripinnis (Blackfin pearlfish) summary
Male or femalecorrected
Legacy female 'Plain brown' is wrong: females are spotted.
TropicalFreshwaterFish.com: Dwarf Argentine Pearl / Cynolebias nigripinnis (hobby care reference) · Aquarium Glaser (F. Schäfer): Austrolebias nigripinnis (importer profile)
Breeding
Diapause: embryos can arrest in up to three stages (DI, DII, DIII; Wourms 1972), the last when fully developed and ready to hatch (Van Dooren et al. 2018, on the related A. bellottii). The FWS quote is from Moshgani and Van Dooren (2011). Legacy claim confirmed.
FishBase: Argolebias nigripinnis (Blackfin pearlfish) summary · US Fish & Wildlife Service: Ecological Risk Screening Summary, Blackfin Pearlfish (Austrolebias nigripinnis) · Aquarium Glaser (F. Schäfer): Austrolebias nigripinnis (importer profile) · Van Dooren et al. 2018, Embryonal life histories: Desiccation plasticity and diapause in the Argentinean pearlfish Austrolebias bellottii (Ecology and Evolution; PMC6262906)
Eggs and youngcorrected
Legacy 'dry 3-6 months' overlaps but FishBase gives 2-4 months; no source gives egg counts ('many').
FishBase: Argolebias nigripinnis (Blackfin pearlfish) summary · TropicalFreshwaterFish.com: Dwarf Argentine Pearl / Cynolebias nigripinnis (hobby care reference) · Aquarium Glaser (F. Schäfer): Austrolebias nigripinnis (importer profile)
Storycorrected
Legacy 'from Argentina' widened to the full range. 1908 importation from an importer profile (not independently confirmed).
Aquarium Glaser (F. Schäfer): Austrolebias nigripinnis (importer profile) · Eschmeyer's Catalog of Fishes: species in genus Argolebias