black tetra

Gymnocorymbus ternetzi
  • Gymnocothymbus ternetzi
  • Tetragonopterus ternetzi
  • Gymnocothymbus ternetzi
  • Tetragonopterus ternetzi
Family Characidae
Genus Gymnocorymbus
IUCN category (World) LC
Gymnocorymbus ternetzi Gymnocorymbus ternetzi

Introduction

Descriptor : Boulenger, 1895

Gymnocorymbus ternetzi, commonly known as black tetra, is a species of freshwater fish belonging to the Characidae family. It is naturally found in the basins of Paraguay and Guaporé, up to Argentina, with introduced populations in the upper Paraná and Paraíba do Sul. Its scientific name honors Carl Ternetz, a Swiss ichthyologist who collected specimens in South America.

Who is it?

Morphology

  • Average size
    5 cm
  • Maximum size
    7 cm
  • Longevity
    6 year
  • Average size
    5 cm
  • Maximum size
    7 cm
  • Longevity
    6 year

How to recognize This fish ?

The body has a fusiform silhouette, with a silvery coloration at the base, marked by two black vertical stripes behind the operculum. The posterior half of the body, including the dorsal and anal fins, is intensely black, which tends to become grayish with age. The anal fin is long and flowing, resembling a skirt. The mouth is terminal.

Sexual dimorphism

Males are slightly smaller than females, with a wider front anal fin; females have a more rounded body, especially during the breeding season.

Behaviour & Life cycle

  • diet
    carnivorous
  • Sociability
    living in shoals
  • territorial
    No
  • Way of living
    diurnal

Gymnocorymbus ternetzi is a gregarious species, living in subtropical freshwater. It occupies the middle and upper layers of the water. Its diet is omnivorous, consisting of worms, small crustaceans, and insects.

Reproduction

  • Reproduction
    ovipare qui pond en eau libre

Reproduction occurs in several annual cycles, with fragmented spawning. Spawning takes place at daybreak, lasts about three hours, and ends with the release of 300 to 400 eggs. The eggs are slightly adhesive, demersal, and spherical. Hatching occurs 20 to 21 hours after spawning, at an average temperature of 24°C. The larvae's mouth opens three days after hatching, once the yolk sac is absorbed. Metamorphosis into juveniles is completed one month after hatching.

Harmless species

The species is harmless to humans. No venom, urticating spine, toxin, or aggressive behavior is documented.

Origin and distribution

Geographic distribution & Conservation

The species is native to the basins of Paraguay, Guaporé, and Paraná, with introduced populations in the upper Paraná and Paraíba do Sul. It is also found in the Pantanal.

Conservation status of populations (IUCN)

World : LC

Where to see this species?

What is its habitat?

Natural environment characteristics

  • Temperature
    20 - 26 °C
  • pH (acidity)
    5.8 - 7.5
  • gh (hardness)
    8 - 12
  • Flow
    Slow and Stagnant

Biotope presentation

This species frequents shallow lakes and lagoons with abundant aquatic vegetation, sedimentary bottoms, open swimming areas, and plant refuges. The water temperature ranges from 20°C to 26°C.

Species of the same biotope

Main recommendations for fishkeeping

Deontology

In order to preserve wildlife, if you acquire this animal, it must not be released into the wild. See also, the Fishipedia charter.

Fishipedia supports the practice of responsible and environmentally friendly aquarium keeping. We encourage maintenance if it is motivated by a desire to understand the biological functioning of living things and if it is done with respect for animal life.

We believe that aquaristics is an opening to the discovery of aquatic environments, especially freshwater, and that this knowledge is necessary to better protect and respect these environments. Logically, we refute the compulsive purchase of animals that would not find a sufficient and / or adapted place in the host aquarium.

Our recommendations

  • Min volume
    120 liters
  • Population min
    10
  • Temperature
    20 - 26 °C
  • pH (acidity)
    6.8 - 7.2

Characteristics

  • Difficulty breeding
    easy
  • Robustness
    tolerant
  • Behaviour
    slightly aggressive
  • Availability
    standard

Recommended equipment from our partners

General reminders

It is strongly advised to read the complete dedicated file and to get information on the feedbacks of maintenance of the envisaged animal, this to avoid any potential conflict whose end result is generally the death of the individual (or the other inhabitants). It is important not to overload your aquarium to limit pollution. This will make maintenance easier.

In nature, animals are subject to weather conditions and live in waters with variable characteristics. The recommendations offered by our team for aquarium maintenance are a guidance and cannot be assimilated to scientific datas.

General reminder on maintenance datas

Le démarrage d'un aquarium est une partie primordiale pour l'équilibre et le bien-être des poissons. Lorsque l'on met en eau un aquarium, l'eau passe naturellement par un cycle biologique : le cycle de l'azote. Celui-ci dure environ trois semaines. Tous les 2 jours, nous vous conseillons de tester votre eau jusqu'à ce que le taux de nitrite soit à zéro pendant plusieurs jours d'affilée.

Pour accélérer ce cycle, vous pouvez utiliser un activateur de bactéries comme JBL Denitrol. Cette solution riche en bactéries vivantes et enzymes permet une mise en place rapide du cycle de l'azote. Les poissons peuvent alors être introduits plus rapidement.

Il est important de tester l'eau de son aquarium régulièrement pour maintenir un environnement sain pour les poissons et les autres habitants. Les tests d'eau permettent de mesurer les niveaux de différents paramètres tels que le pH, la dureté totale, ainsi que les taux de nitrates, de nitrites et d'ammoniaque.

Pour réaliser ces tests, vous pouvez utiliser des produits d'analyse spécialisés tels que JBL ProScan qui permet de réaliser un diagnostic de l'eau directement via un smartphone. Il existe également des coffrets de tests plus classiques de bandelettes, comme JBL PROAQUATEST.

En cas d’usage de l’eau du robinet, vous pouvez utiliser un conditionneur d’eau de type Biotopol de JBL pour éliminer les substances nocives comme le chlore, le cuivre, le plomb et le zinc. Une eau trop dure ou trop calcaire peut être inadaptée à de nombreuses espèces tropicales d’eau douce. Si nécessaire, vous pouvez la couper avec de l’eau osmosée ou de pluie filtrée afin d’obtenir une dureté plus adaptée aux besoins de vos poissons et de vos plantes. Les conditionneurs d'eau garantissent une meilleure santé aux poissons et une meilleure croissance des plantes.

Chlorine and chloramine are dangerous for the health of animals. Used to disinfect water, these agents are present in significant quantities in tap water. We recommend using an anti-chlorine agent every time you change the water. In addition to chlorine, treatments and medicines sold for aquarium use sometimes contain dangerous heavy metals in high doses.

Specific needs for the black tetra

The black tetra is a species which lives naturally at a temperature between 20 °C and 26 °C. Nitrate levels should remain below 50mg/L. To keep the water clean and unpolluted, plan on changing 20% to 30% of the water volume each month.

Breeding this species is accessible to any hobbyist. It is recommended to follow some basic rules and to be rigorous to achieve a good maintenance.

This species is particularly common in the aquarium trade. Animals from long-term breeding are usually acclimatized at a temperature of about 26 °C in neutral water.

Cohabitation & Environment

Being a living in shoals fish, it is advisable to install at least 10 individuals in an aquarium of 120 liters minimum. Group maintenance is a prerequisite to ensure their well-being. Lonely individuals tend to quickly become stressed and become especially susceptible to disease. Warning, mixing several species living in the same living area is not recommended if the volume is not significant.

Tips for feeding

The black tetra is carnivorous.

This species can eat dry food (flakes, pellets), fresh food and frozen food. To avoid deficiencies, it is recommended to vary the types of food.

Feed animals in moderation to maintain good water quality. Meals should be eaten within 2–3 minutes, served in several small portions rather than a single large ration.

Uneaten food quickly decomposes, releasing ammonia, nitrites, and nitrates, which disturb the aquarium’s biological balance.

Make sure each species can access food properly, slower or bottom-dwelling individuals may require targeted feeding.

Food recommendations from our partner JBL - Products PRONOVO

Reproduction protocol

  • Maintenance difficulty
    moderate
  • egg-laying protection
    No

Hybridization risks

In general, it is advised not to mix several species of the same genus or different varieties of the same species, to avoid the risks of hybridization.

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To go further

Species of the same family

To read on the web

Partner websites

Sources & Contributions

Participation & Validation

The Fishipedia team and specialist contributors are committed to providing high-quality content. However, although the information comes from scientific sources or testimonials from specialists, the cards may contain inaccuracies.

Benoit Chartrer

Benoit Chartrer

Translation

Translation done with the valuable contribution of our translators, who make this information available to a wider audience. We sincerely thank them for their commitment.

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Template and content © Fishipedia - Unauthorized reproduction without prior request - ISSN 2270-7247 - Last modification 12/11/2023

Where to see this species?

Scientific partners

Species of the same family

Species of the same biotope

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