False Black Tetra

Gymnocorymbus thayeri

Photo of aquarium fish False Black Tetra
Natural range
  • Amazon River Basin
  • Orinoco River Basin
  • Bolivia
  • Brazil
  • Colombia
  • Guyana
  • Trinidad and Tobago
Characins Cold-water Conservation status: Least concern LC

Family:Acestrorhamphidae

The False Black Tetra, also known as the Blue-spotted Gymnocorymbus (scientific name Gymnocorymbus thayeri), belongs to the Acestrorhamphidae family. It was named in honor of the patron N. Thayer, who supported a large-scale ichthyological expedition to South America in 1865–1866.

Required aquarium volume
from 100 L
Size in aquarium
5 cm
Temperature
19 – 24 °C
Temperament
Peaceful (regular)
Parameters
Temperature19 – 24 °C
Water pHSlightly acidic (5.5) – Neutral (7.3)
Water dHSoft (4) – Very hard (18)
Water salinityno salt (freshwater)
Size in aquarium5 cm
Lifespan4 years
TemperamentPeaceful (regular)
Toward small fishnot a predator
Required aquarium volumefrom 100 L
Lightingdimmed or moderate
Substrateany (no restrictions)
Water flowweak
FeedingSmall
KeepingMedium group

Frequently asked questions

The essentials: size, tank volume, water parameters and care

How big does False Black Tetra get?

An adult reaches 5 cm in length. Plan the tank around the maximum size: the fish quickly outgrows a cramped setup.

What size aquarium does False Black Tetra need?

The recommended volume is 100 L. A smaller tank speeds up nitrate build-up and raises stress levels.

What water parameters does False Black Tetra need?

Temperature 19–24 °C, pH 5.5–7.3, hardness 4–18 dGH. Stability matters more than exact values: sudden swings are harder on the fish than a small deviation from the ideal.

How long does False Black Tetra live?

Around 4 years when kept properly. Lifespan depends directly on tank volume, water quality and a varied diet.

Is False Black Tetra aggressive?

Temperament: peaceful (regular). Keep this in mind when choosing tank mates.

How many False Black Tetra should be kept together?

Recommended setup: medium group (6–8 individuals). Ignoring this is a common cause of stress and disease.

What does False Black Tetra eat?

Diet type: small / appropriate size / pieces. Feed small portions that are finished within a couple of minutes — overfeeding does more harm than underfeeding.

What is the scientific name of False Black Tetra?

The scientific name of the species is Gymnocorymbus thayeri, family Acestrorhamphidae.

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