Penguin Tetra (Thayeria boehlkei)

Thayeria boehlkei is native to the Peruvian Amazon, particularly the Madre de Dios River and adjacent tributaries, where it inhabits slow-moving, vegetated rivers and flooded areas. The species was named in honor of James Erwin Böhlke, an American ichthyologist at the Academy of Natural Sciences in Philadelphia.

The common name 'Penguin Tetra' and the alternative 'Hockey Stick Tetra' both reference the distinctive bold black marking: a horizontal black stripe runs from the midlateral line rearward through the base of the lower caudal fin lobe, continuing into the tip of the lower tail — creating a distinctive hockey-stick-shaped marking and a strong black-and-white contrast pattern reminiscent of a penguin's formal coloration.

Thayeria boehlkei is also immediately recognizable for its characteristic resting posture: it typically maintains a slight head-up, body-angled orientation in the water column, unlike most tetras that swim horizontally. This posture is maintained at rest and during slow swimming, while high-speed bursts are fully horizontal. The origin of this behavior is thought to relate to feeding at the surface.

Reaching 6–7 cm, Penguin Tetras are medium-sized tetras that are robust, hardy, and easy to keep. They are active swimmers that school energetically in open water and make an eye-catching addition to community planted aquariums.

Penguin Tetras are adaptable and hardy: pH 6.0–7.5, hardness 3–15 dGH, and temperatures 22–28°C. They tolerate a range of conditions and are suitable for both beginner and experienced aquarists.

A minimum 100-liter aquarium with significant open swimming space suits a group of 8–10. Dense plantings along the tank perimeter with open central swimming lanes allow natural schooling behavior. Moderate current is appreciated — they are active, strong swimmers.

Feed quality flake food, micro pellets, and supplements of live or frozen foods: daphnia, brine shrimp, cyclops, and small bloodworms. They are enthusiastic, active feeders that readily accept most aquarium foods.

Penguin Tetras are peaceful and compatible with most community species: other medium tetras, corydoras, small catfish, livebearers, gouramis, and peaceful cichlids. Avoid nippy species or very small fish.

Keep in groups of at least 8–10 for natural schooling behavior and to observe the collective angled posture that makes this species unique. Weekly water changes of 25–30% maintain water quality.