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Emperor Tetra

Scientific Name: Nematobrycon palmeri
Family: Characidae, Nematobrycon Clade

About the Emperor Tetra

Species Type: Freshwater Fish
Category: Characins

Care Level: Easy. Does well in a slightly more narrow range of water parameters and shouldn't be used to cycle an aquarium. Will eat most prepared foods. May have some specific care requirements in terms of particular water parameters, social behaviors, food items etc.

Origin: Rio San Juan and Rio Atrato basins in western Columbia, South America. Occurs in sluggish tributaries and small quiet rivers and streams.

Compatibility/Temperament: Generaqlly peaceful, though males can be territorial but rarely causing damage to each other; they may however become real bullies to other similar fish (tetra, rasbora, etc). Must be in a group of at least six but preferably nine or more. Suitable in community tanks with angelfish, other characins, dwarf cichlids, small catfish and loaches, gourami, rasbora and danios.


This species does not like brightly-lit or sparse environments. In a well-planted aquarium with low light their colours intensify substantially. Prefers the middle and upper levels in the water column. Needs to be in groups but frequently swims individually. This genus lacks an adipose fin.

Males are larger, more colourful, and develop extended dorsal, caudal and anal fins; males have a blue iris (eye) while females are more green. Will easily spawn in a tank planted with fine leaved plants, very dimly lit, and soft and acidic water. Adults will readily eat the eggs after spawning, but in well-planted tanks sevweral fry will likely survive. This species is very prolific. Males, especially when courting females--and this is almost continually--can be very aggressive to other fish.

This species was described in 1911 by C.H. Eigenmann who erected the genus; the name is derived from the Greek for "Brycon with threads," a reference to the extended filaments of the caudal fin.

Another "species," Nematobrycon amphiloxus, was identified and named by Eigenmann & Wilson (1914) and has sometimes been referred to as the "black emperor tetra." This is now believed to be a colour morph of the subject species, and the name N. amphiloxus now considered a synonym for N. palmeri and not a valid species (Pavanelli in Reis et al., 2003). The "Rainbow Emperor Tetra" is a distinct species, N. lacortei. The so-called "Blue Emperor" is Inpaichthys kerri, not closely related to Nematobrycon.

The genus Nematobrycon was previously considered within the Sub-Family Tetragonopterinae, but this classification, as indeed that of the entire Characidae family, has for some time been deemed incertae sedis [Latin for "of uncertain placement"]. Javonillo, et al. (2010) proposed that the Subfamily Tetragonopterinae should only be used for species within the genus Tetragonopterus. J. Marcos Mirande (2009) proposed several revisions to the Family Characidae based upon phylogenetic diagnosis. Some genera have been moved to a new Subfamily, while others are now (temporarily) assigned to a specific clade within the Family pending further phylogenetic study.


Javonillo, Robert, Luiz R. Malabarba, Stanley H. Weitzman and John R. Burns (2010), "Relationships among major lineages of characid fishes (Teleostei: Ostariophysi: Characiformes), based on molecular sequence data," Molecular Phylogenetics and Evolution, Vol. 54, No. 2 (February 2010).

Mirande, J. Marcos (2009), "Weighted parsimony phylogeny of the family Characidae (Teleostei: Characiformes)," Cladistics, Vol. 25, No. 6 (July 2009).

Emperor Tetra Diet

In nature it feeds on worms and crustaceans; readily accepts most prepared foods including flake and frozen foods like daphnia and bloodworms.


Reaches 2 inches.

Minimum Tank Suggestion

30 inches in length.

Ideal water parameters for Emperor Tetra

Soft to moderately hard (hardness to 20 dGH) acidic to slightly basic (pH to 7.5) water, temperature 23-27C/73-81F. In basic water its colours will not be as intense; prefers less than 10 dGH and pH 5-6.6.

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