Nematobrycon palmeri
A placid tetra from Colombia with striking sexual dimorphism.
Nematobrycon palmeri, called the emperor tetra, is a freshwater ray-finned fish from the family Acestrorhamphidae. It lives in the Atrato and San Juan river basins of western Colombia. First brought to the United States for the aquarium trade in 1960, it quickly became popular. The species is named after Mervyn George Palmer (1882–1954), an English traveler who collected the type specimen in Central and South America for the British Museum.
The fish has a long, slim, flattened body that reaches about 3 inches (76 mm) when mature. Its purple color shows best in a tank with floating plants and dim light; too much brightness makes the yellow tones dominate. A black line runs inside a blue stripe from the eye to the tail. The sickle-shaped dorsal fin, along with the pectoral and anal fins, are yellow. Males are larger than females and have longer anal fins and a more pointed tail. The sexes are easy to tell apart: males have metallic blue eyes, while females have metallic green eyes. Males also have a three-pronged tail, with the central black stripe often extending beyond the rest of the tail; in females, this stripe usually stops at the clear part of the tail. However, this tail feature is not always reliable, as the third prong can be nipped off in fights with tank mates, and dominant females may grow the extension too. The emperor tetra should not be confused with the royal tetra (Inpaichthys kerri), which looks similar and shares some common names.
An omnivore, the emperor tetra eats both plant and animal matter. A good flake or pelleted food forms the base of its diet, but it benefits from live foods like daphnia and mosquito larvae, as well as frozen foods such as bloodworms.
In a large, well-planted aquarium, a single pair often breeds without extra help. If no other fish are present, some fry may survive, especially if the parents are well fed. The young find natural food like protozoa and algae in the tank, and screened daphnia or dry fry food can supplement their diet as they grow.
The emperor tetra is a calm fish that gets stressed by more active species. It reaches 4.2 cm (1.7 in) in length. It prefers a pH of 6.5, hardness of 3–6 dKH, and a temperature of 23–27 °C (73–81 °F). Unlike most tetras, it does not school readily; a pair seems more content than a group.
Quick Facts
- Taxon
- Nematobrycon palmeri
Facts from the source article.
Lore & Background
The emperor tetra was named in honor of Mervyn George Palmer (1882–1954), an English traveler who collected in Central and South America for the British Museum and collected the type specimen. Its body is long, slim, and flattened, reaching about 3 inches (76 mm) at maturity. The purple hue becomes more apparent in aquariums with floating plants and subdued lighting; if too bright, yellow coloration dominates. A black line within a blue stripe runs from eye to tail, and the sickle-shaped dorsal, pectoral, and anal fins are yellow.
Males and females are highly sexually dimorphic. The most reliable distinction is eye color: males have metallic blue eyes, females metallic green. Males are larger with longer anal fins and a more pointed caudal fin, including a three-pronged tail where the medial black stripe usually extends beyond the rest. However, this tail feature can be unreliable, as the third prong may be nipped off in competition or dominant females may grow the extension. The species should not be confused with the royal tetra Inpaichthys kerri.
Emperor tetras are omnivores, accepting flake or pelleted food, and benefit from live foods like daphnia and mosquito larvae as well as frozen bloodworms. They are placid and disturbed by boisterous species. They do not school as readily as most tetras; a pair appears happier, though a large group may school for several minutes after addition of fresh cool water.
Reader's Guide
The emperor tetra is notable for its striking sexual dimorphism, which allows easy differentiation between males and females primarily by eye color—a trait not common among tetras. Its placid nature makes it suitable for community tanks with similarly peaceful species, though it may be disturbed by boisterous tank mates. The species does not school as readily as most tetras, and a pair often appears more content, but a large group can be induced to school briefly with cool water changes. Breeding can occur spontaneously in a well-planted aquarium without extra stimulation, and if no other fish are present, some young may survive by feeding on natural protozoa and algae, supplemented by screened daphnia and dry fry food. The emperor tetra's coloration is influenced by lighting: subdued light and floating plants enhance its purple hue, while bright light emphasizes yellow. Its history includes importation to the United States in 1960 and naming after a British Museum collector. The species is sometimes confused with the royal tetra Inpaichthys kerri, which shares similar common names.
Did You Know?
- The emperor tetra was first imported to the United States in 1960.
- It does not school as readily as most tetras, but a large group may school briefly after cool water is added.
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