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Family: Characidae, Sub-Family Aphyocharacinae

Common Name: Kerri Tetra, Royal Tetra, Blue Emperor Tetra

Origin and Habitat: Amazon Basin, Brazil: Rio Aripuana, upper Rio Madeira basin.

Compatibility/Temperament: A peaceful and social tetra, it must be maintained in a group of minimum 5 but preferably a few more. Suitable for community aquaria with similar small, peaceful fish such as other tetras, rasbora, pencilfish, dwarf cichlids, catfish, loaches, gourami.

Kerri Tetra Diet

Omnivore; these tetras are rather greedy so anything will be relished. Be sure not to overfeed!


Minimum Tank Suggestion

24 inches in length

Water parameters for Kerri Tetra

Soft (hardness to 10 dGH) and slightly acidic (pH up to 7.0) water, temperature 24-27C/75-81F.


A tank furnished with several plants and driftwood with some leaf litter and tannic acids provided by driftwoods and peat filtration will make an excellent tank environment for these little fish. It prefers well-planted aquaria, but swimming room must be provided. This tetra will do best when kept in a group in soft, slightly acidic water but will still adapt to various water conditions so long as they are properly acclimated to it and the water is not too hard. In non-planted tanks, or with different water parameters, the colours will not be defined and it will appear washed out.

A ready spawner when conditions are to its liking, the sexes are easily identified by the colour of the adipose fin; on males it is blue, but on females it is reddish-orange. The male also has a luminous blue sheen over the body. These characteristics can be seen in the accompanying photos, the first of which depicts a male and two females.

This fish is sometimes commonly named the Blue Emperor Tetra, though it is not closely related to the true "Emperor" tetra Nematobrycon palmeri nor N. lacortei. The kerri tetra possesses an adipose fin, which is absent on both Nematobrycon species.

This species was described by Gery & Junk in 1977 who erected the genus at that time with the subject fish as the type species. The genus name is a dedication to a Brazilian institution about Indian tribes. To date, this is the only species in the genus.

The genus Inpaichthys was previously considered within the subfamily Tetragonopterinae, but this classification has for some time been deemed incertae sedis [Latin for "of uncertain placement"]. In a study published in 2010 (Javonillo, et al, 2010), it was determined that the subfamily Tetragonopterinae should only be used for species within the genus Tetragonopterus. Also, 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) assinged to a specific clade within the family pending further study.


Gery, Jacques and W.J. Junk (1977), "Inpaichthys kerri n. g. n. sp., um novo peixe caracideo do alto rio Aripuana, Mato Grosso, Brasil," Acta Amazonica v. 7 (no. 3), pp. 417-422.

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).

Tagliacollo, V.A., R. Souza-Lima, R.C. Benine and C. Oliveira (2012), "Molecular phylogeny of Aphyocharacinae (Characiformes, Characidae) with morphological diagnoses for the subfamily and recognized genera," Molecular Phylogenetics and Evolution, 64, pp. 297–307.

Contributing Members

The following members have contributed to this profile: Byron


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