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EveryFish
Thayeria boehlkei

Penguinfish

Small striped characin from South American rivers

Photo: Juan R. Lascorz, CC BY-SA 3.0, via Wikimedia Commons

Thayeria is a genus of small freshwater fish in the family Acestrorhamphidae. These peaceful characins live in tropical South America, including the Amazon Basin. They are known for their distinct lateral black stripe and unique body shape.

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  • Genus of small freshwater characins
  • Found in Amazon and Maroni Rivers
  • Distinctive single black lateral stripe
  • Peaceful temperament suitable for tanks
  • Includes blackline penguinfish species

What it is

Thayeria is a genus of ray-finned fishes within the family Acestrorhamphidae, also known as American characins. These fish are small and possess a distinctive vesica piscis shape, which resembles a swim bladder or oval form. A single black stripe runs along the side of their bodies. They are generally peaceful in nature. The genus includes species such as the blackline penguinfish and the common penguinfish.

Where it lives

These fishes inhabit freshwater systems in tropical South America. Their range covers the Amazon Basin. They are also found in the Approuague River and the Maroni River. These locations provide the warm, fresh water environments that the genus requires for survival.

How it lives

Members of this genus are described as peaceful. They share their habitat with other freshwater species in the Amazon and surrounding river systems. Specific details on their diet, schooling behaviour, or predators are not provided in the available records. Their calm disposition makes them suitable for community settings.

Breeding and life cycle

Consequently, no specific details about their reproductive cycle or juvenile stages can be provided here.

Penguinfish
A drawing made by EveryFish from what this page says. It is a diagram, not a picture of the real fish.

Fish and people

The blackline penguinfish and related species are kept by enthusiasts. Their small size and peaceful nature make them appropriate for aquariums.

Status and threats

Data on their population trends is absent.

Penguin Tetra (Thayeria boehlkei)
Penguin Tetra (Thayeria boehlkei). Photo: Kkonstan, CC BY 3.0, via Wikimedia Commons

Questions people ask about Penguinfish

Where do penguinfish live?

They are found in freshwater habitats in tropical South America. Their range includes the Amazon Basin as well as the Approuague and Maroni Rivers.

Are penguinfish aggressive?

No, members of the Thayeria genus are described as peaceful. This trait makes them suitable for community aquariums where they coexist with other non-aggressive species.

What do penguinfish look like?

They are small fish with a vesica piscis shape. A key identifying feature is the single black stripe that runs horizontally along the side of their body.

Good reading and sources

Where this page comes from

The facts on this page come from the Wikipedia article "Thayeria", written by its contributors and used under the CC BY-SA 4.0 licence, and from its Wikidata record (CC0). EveryFish rewrote the text in its own words, with AI assistance, and compares every page with the article to make sure no passage is copied. It may be reused under the same CC BY-SA 4.0 licence with a link back.

It may contain mistakes, and figures change over time. Nothing here is investment or buying advice. If something is wrong, tell us. Last refreshed 2026-11-15.

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Photo credits on this page

The small pictures above come from Wikimedia Commons under free licences. Some are cropped to fit.

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