Penguin Tetra

The penguin tetra is recognized by the thick black line that starts behind the gill cover, runs along the body and curves down into the lower lobe of the tail; this line resembles a hockey stick. When at rest it holds a slanted posture with its head slightly raised. Because of this posture and its black-and-silver look, it was given the name "penguin."

It is a hardy, inexpensive species; farm-bred fish are easy to find. With its active nature and its liking for swimming in open water, it brings the middle and upper layers of the aquarium to life.

It lives in slow-flowing branches and floodplains of large rivers in the Amazon basin in Peru and Brazil, usually in planted areas close to the surface.

• Volume: at least 80 liters for a school of 6–10; a length of 80 cm is recommended.
• Water: 23–27°C, pH 6–7.5, soft to moderately hard water.
• Lid: it may leap out of the water when startled; a lid is essential.
• Decor: plants along the edges, floating plants on part of the surface, a large open area in the middle.
• Maintenance: a 25% water change every week; gentle to moderate flow is tolerated.

Omnivorous. It readily takes flakes and granules at the surface or in midwater. Vary it with frozen brine shrimp, bloodworms, daphnia and mysis shrimp. Feed 1–2 meals a day, only as much as is eaten within a few minutes; because it has a big appetite, avoid overfeeding.

Peaceful but active; small chases are seen within the school. It usually does not harm other species, but its activity may unsettle very small and skittish species. It usually leaves adult shrimp alone.

Good companions: medium-sized tetras, rasboras, danios, corydoras, plecos, gouramis, peaceful cichlids.

Avoid: large predators that could fit it in their mouths, very small nano species, aggressive cichlids.

A school of at least 6, ideally 10 is recommended. In a large group the fish swim together in open water and their slanted posture becomes more noticeable. The sex ratio does not matter. When kept in small numbers the school breaks up and the fish become more skittish.

It is an egg scatterer and quite prolific. A separate tank is prepared with soft, slightly acidic water and fine-leaved plants; the female lays a large number of eggs. The parents are removed after spawning. The fry are fed infusoria, then newly hatched brine shrimp.

• Losses from jumping: the most common cause of death in tanks without a lid.
• White spot (ich): may appear after transport.
• General: it is hardy; with regular water changes it rarely causes problems.

Females are larger with a plumper belly; the difference becomes clear especially when they are carrying eggs. Males are more slender.