Redtail Penguin Tetra

The Redtail Penguin Tetra, scientifically known as Thayeria sp. “Redtail (Teles Pires),” is an undescribed penguin tetra collected from the Rio Teles Pires in the upper Tapajós basin of Mato Grosso, Brazil. It inhabits clear, well-oxygenated tributaries with sandy bottoms, leaf litter, and submerged wood along gently flowing margins. Unlike the standard aquarium penguin tetra, this wild form is noted for its vivid reddish caudal fin.

Adult Redtail Penguin Tetras typically reach about 1.8 to 2.2 inches (4.5 to 5.5 cm) in length. The body is silvery to pale gold with the signature diagonal black “penguin” stripe that begins behind the gill cover, angles downward, and continues through the tail. The caudal fin is distinctly red to orange-red, especially in settled, well-conditioned fish. Males are usually a touch slimmer and show slightly stronger color.

A tank of at least 20 gallons is suitable for a small group. The aquarium should provide open swimming space with dense planting or wood and leaf litter around the edges. A dark substrate, driftwood, and a bit of surface cover help calm the fish and intensify color. Gentle to moderate flow and good oxygenation reflect their clearwater origins.

Water parameters should include a temperature of 74 to 80°F (23 to 27°C), a pH between 5.8 and 7.2, and soft to moderately hard water. Stable, clean conditions with regular partial water changes will keep the Redtail Penguin Tetra at its best.

Feeding Thayeria sp. “Redtail (Teles Pires)” is straightforward. Offer high-quality micro pellets or flakes and frequent small portions of live or frozen fare such as daphnia, cyclops, and baby brine shrimp to deepen color and condition.

Redtail Penguin Tetras are peaceful, active midwater fish that should be kept in groups of eight or more to reduce skittishness and show natural shoaling. Suitable tankmates include other small, calm characins, pencilfish, Corydoras, and dwarf Apistogramma; avoid large or boisterous species.

Breeding is possible but uncommon. As typical egg-scattering tetras, they spawn among fine-leaved plants or mops with no parental care. A separate soft, slightly acidic, dim tank improves success; remove adults after spawning and start fry on infusoria before transitioning to newly hatched brine shrimp.

Thayeria sp. “Redtail (Teles Pires)” (Redtail Penguin Tetra) is a striking, wild-origin penguin tetra that brings distinctive red tail flashes and classic “penguin” patterning to planted and blackwater-style South American aquariums.