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Family: Characidae, Hemigrammus Clade

Common Names: January Tetra, Costello Tetra

Origin and Habitat: Central and upper Amazon basin through Brazil and Peru, and Lake Hyanuary near Manaus, Brazil. Inhabits slow-moving streams and floodplain lakes.

Compatibility/Temperament: Peaceful, somewhat quiet fish, suitable in a community tank of similar characins, rasbora, small catfish and loaches, dwarf cichlids, gourami. Must be in a group of at least six.

Costello Tetra Diet

Accepts prepared foods including flake and frozen.


Grows to 1.6 inches.

Minimum Tank Suggestion

20 inches in length

Water parameters for Costello Tetra

Soft to moderately hard (hardness to 15 dGH), acidic to slightly basic (pH below 7.5) water, temperature 23-27C/73-81F. Tends to lose colour in basic harder water.


This lovely fish is sometimes confused with the Head & Tail Light Tetra due to the similarity in the glowing spot on the caudal peduncle, but should be easily distinguished by its slender profile as opposed to the deeper body of the Head and Tail Light Tetra. It also has a greenish-yellow iridescent line laterally along the body somewhat akin to the "neon" tetras. It is a hardy fish once acclimated, and appreciates regular water changes. Well suited to a planted tank.

Males are a bit smaller and slimmer than females, and have a small hook on the anal fin that is absent in females. Will spawn with normal characin methods, and adults will eat the eggs if not removed.

The common names of this species vary, and include "Green Neon" which is very confusing, as this fish is not closely related to Paracheirodon simulans. "January Tetra" is an English rendering of the scientific name which was given to the fish when first described by Durbin in 1918 since the specimens came from Lake Hyanuary (January) in Brazil. Most fish in the hobby now come from commercial breeders.

The genus Hemigrammus--the name from the Greek meaning "with half line," a reference to the incomplete lateral line--was erected as a subgenus of Poecilurichthys by T.N. Gill in 1858 but has been recognized as a distinct genus since Gery (1977). There are presently about 50 valid species. The classification is deemed incertae sedis [Latin, "of uncertain placement"]. It was formerly considered within the subfamily Tetragonopterinae, but Javonillo (2010) suggest that this subfamily should be restricted to species within the genus Tetragonopterus since they do not share physiological characteristics with species in other genera such as Hemigrammus.

None of the diagnostic characteristics presently used to describe species in Hemigrammus, including the incomplete lateral line which gave rise to the genus name, are unique to the genus. Mirande (2009) states that the genus is not monophyletic, a view shared by most ichthyologists working with the characidae. [A monophyletic genus is one wherein the species share a common ancestor, thus linking them together physiologically.] Mirande has 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 study.

Hemigrammus has until recently been differentiated from Hyphessobrycon solely on the basis of the fish in Hemigrammus possessing a scaled caudal fin; this however is now known to be unreliable, since it occurs in intermediate conditions (de Lucina, 2003).


de Lucena, Carlos Alberto Santos (2003), "A new characid fish, Hyphessobrycon scutulatus, from the Rio Teles Pires drainage, upper Rio Tapajos system (Ostariophysi: Characiformes: Characidae)," Neotropical Ichthyology 1 (2), pp. 93-96.

Gery, Jacques (1977),"Characoids of the World, TFH Books.

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).

Contributing Members

The following members have contributed to this profile: Byron


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