Penguin Tetra

The Penguin Tetra (Thayeria boehlkei) is a distinctive and active freshwater schooling fish, instantly recognisable by its bold black diagonal stripe and unique angled swimming posture. Hardy and peaceful, Penguin Tetras are an excellent choice for community aquariums and are well suited to both beginner and experienced aquarists.

This species is highly social and displays its best behaviour and appearance when kept in groups. Penguin Tetras are constant swimmers that occupy the mid to upper levels of the aquarium, adding movement and contrast to planted and open-water setups.

Physical Characteristics

• Adult Size: Approximately 6–7 cm (2.5–3 inches)

• Coloration: Silver body with a strong black diagonal stripe running from the eye to the tail

• Body Shape: Slender, torpedo-shaped tetra profile

• Sexual Dimorphism:

  • Females are slightly larger and deeper-bodied

  • Males are slimmer with more streamlined profiles

Behaviour & Temperament

• Temperament: Peaceful

• Tank Level: Mid-water

• Schooling Behaviour: Must be kept in groups of 6 or more

• Activity Level: Active but non-aggressive

• Temperament: Peaceful

• Tank Level: Mid to upper water column

• Schooling Behaviour: Must be kept in groups of 6 or more

• Activity Level: Very active swimmer

Suitable Tank Mates

• Other peaceful tetras

• Rasboras

• Corydoras catfish

• Dwarf gouramis

• Peaceful livebearers

Avoid:

• Aggressive or highly territorial fish

• Fin-nipping species

• Large predatory fish

Breeding Information

• Spawning Type: Egg scatterer

• Breeding Setup:

  • Fine-leaved plants or spawning mops

  • Soft, slightly acidic water improves success

• Parental Care: None

• Notes: Adults may eat eggs; removal is required for breeding attempts

Special Considerations

• Requires swimming space due to constant movement

• Best colour and behaviour shown in larger groups

• Sensitive to poor water quality despite general hardiness

• Strong filtration acceptable, but avoid extreme currents

Aquarium Requirements

• Minimum Tank Size: 80 litres for a small school

• Water Temperature: 22–27°C

• pH Range: 6.0–7.5

• Water Hardness: 2–15 dGH

• Substrate: Sand or fine gravel

• Decor: Live plants, driftwood, shaded areas

• Filtration: Moderate, well-maintained

• Lighting: Moderate; plants help diffuse brightness

Diet & Feeding

• Diet Type: Omnivore

• Recommended Foods:

  • High-quality flakes or micro pellets

  • Frozen foods such as daphnia and brine shrimp

  • Occasional live foods for conditioning

• Feeding Frequency: Once or twice daily in small portions

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