Penguin Tetra - Thayeria boehlkei

Penguin Tetra (Thayeria boehlkei)

The Penguin Tetra is an attractive and unusual freshwater shoaling fish recognised for its distinctive black diagonal stripe and characteristic head-up swimming position. Also known as the Hockey Stick Tetra or Blackline Penguinfish, this peaceful South American species features a slender silver body with a bold black marking extending from the head through the lower section of the tail. Its active swimming behaviour and striking appearance make it a popular addition to planted community aquariums. Penguin Tetras are particularly rewarding when maintained in larger groups, where their coordinated swimming and natural social interactions create an interesting display.

Common Name:
Penguin Tetra, Hockey Stick Tetra, Blackline Penguinfish, False Penguin Tetra

Scientific Name (Latin):
Thayeria boehlkei

Maximum Size:
Approximately 5–6 cm including the tail, although many aquarium specimens remain slightly smaller

Water Type:
Freshwater

Origin / Natural Habitat:
The Penguin Tetra originates from South America, with populations recorded in the upper Amazon River basin of Peru and the Araguaia River drainage in Brazil.

Wild Thayeria boehlkei inhabit freshwater streams, tributaries and sheltered waterways, often associated with dense marginal vegetation, submerged branches and areas of relatively gentle water movement.

These environments provide natural cover and access to small aquatic invertebrates, insects and other food organisms.

In the wild, Penguin Tetras form social groups and occupy the middle to upper regions of the water, where their unusual angled swimming posture is particularly noticeable.

Water Parameters:
Temperature: 22–28°C
pH Range: 6.0–8.0
Hardness: Soft to Moderately Hard
Ammonia/Nitrite: 0 ppm
Nitrate: Kept low and stable

Temperament:
Peaceful

Penguin Tetras are generally peaceful, active shoaling fish that are well suited to established freshwater community aquariums.

They should be maintained in groups of at least 8–10 individuals, with larger groups recommended where space allows. Keeping sufficient numbers encourages natural swimming behaviour and helps reduce occasional chasing or fin-nipping.

Although usually peaceful, Penguin Tetras can occasionally nip the fins of slower-moving or long-finned fish, particularly when kept in small groups.

They are best housed alongside similarly sized, active community species that are unlikely to intimidate them or compete excessively for food.

Diet:
Omnivore

Penguin Tetras naturally feed on small insects, worms, crustaceans and other aquatic invertebrates.

In the aquarium, they readily accept a varied diet of high-quality tropical flakes, fine granules and appropriately sized micro pellets.

Their diet should be supplemented with frozen or live foods such as daphnia, brine shrimp, bloodworm, cyclops and small mosquito larvae.

A varied feeding routine helps maintain healthy growth, natural colouration and good overall condition.

Offer small portions once or twice daily, ensuring all individuals have access to food.

Minimum Tank Size:
Approximately 90 litres

Penguin Tetras are active shoaling fish that benefit from generous horizontal swimming space.

An aquarium measuring approximately 80 cm or more in length is recommended for a group, with larger aquariums preferable for substantial shoals or mixed community setups.

Provide open swimming areas alongside planted sections, driftwood and natural shelter.

Although they are relatively small fish, Penguin Tetras should not be maintained in cramped aquariums where their natural group behaviour is restricted.

Behaviour & Activity:
The Penguin Tetra is best known for its unusual swimming posture, frequently holding its body at a slight upward angle with the head positioned higher than the tail.

This distinctive behaviour, combined with the dark diagonal body stripe, gives the fish its characteristic appearance.

Penguin Tetras are active swimmers that generally occupy the middle and upper regions of the aquarium, moving together in loose shoals.

When maintained in sufficient numbers, they display natural group movement, occasional short chases and interactions between individuals.

They appreciate planted areas and shaded sections but should also have plenty of open water for uninterrupted swimming.

A secure aquarium lid is recommended, as Penguin Tetras may jump when startled.

Community Suitability:
Community Fish

Penguin Tetras are suitable for established freshwater community aquariums containing peaceful, similarly sized fish.

Suitable companions include other peaceful tetras, rasboras, Corydoras catfish, smaller rainbowfish, peaceful dwarf cichlids and appropriately sized bottom-dwelling species.

They are particularly attractive when housed in planted South American community aquariums alongside compatible species.

Avoid large predatory fish, aggressive cichlids and particularly slow-moving or long-finned tankmates that may become targets for occasional fin-nipping.

Maintaining a good-sized group of Penguin Tetras helps distribute social interactions and encourages more settled behaviour within the aquarium.

Special Requirements or Care Notes:
Provide a mature, well-maintained freshwater aquarium with stable water chemistry and efficient biological filtration.

Penguin Tetras are naturally social fish and should be maintained in groups of at least 8–10 individuals, rather than singly or in pairs.

Include a combination of open swimming space, aquarium plants, driftwood and shaded areas to create a comfortable environment.

Floating plants can help diffuse bright aquarium lighting, while darker substrates may enhance their natural colouration.

Regular partial water changes are important, as Penguin Tetras benefit from consistently clean water and low nitrate levels.

Although generally adaptable to different water conditions, sudden changes in temperature, pH or hardness should be avoided.

Offer a varied diet containing quality prepared foods alongside occasional frozen or live foods.

Avoid housing them with slow-moving, long-finned species that may be vulnerable to occasional fin-nipping.

Penguin Tetras are egg-scattering fish, and adults may consume their own eggs. Successful breeding generally requires a separate breeding aquarium with suitable spawning cover.

Most specimens available through the aquarium trade are captive-bred, making them relatively adaptable to established aquarium conditions.

Suitable for:
Beginner to Intermediate

Availability:
Common / Regularly Available

All images are a visual representation of the fish you will receive, made to be as accurate as possible. Please note that Mother Nature is a wonderful thing, and variation in patterns and colours will occur — that is part of the unique beauty of these animals.