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Costello Tetra Fact Sheet

The Costello Tetra, Hemigrammus hyanuary, is native to the Amazon River basin and occurs in Brazil and Peru.  Another very common name for this fish is the January Tetra.

The Costello Tetra has some similarity in appearance to the Head and Tail Light Tetra.  The most obvious difference is that the Head and Tail Light Tetra is a much deep bodied fish.


The Costello Tetra is native to Lake Hyanuary in Brazil as well as to other areas.  The specific name of hyanuary was taken from this lake.  The common name, “January Tetra”, is apparently from the same source on the basis that the English translation of Hyanuary is January.  It certainly looks as if it should be, but I am not convinced that it is.  The language of Brazil is Portuguese, and the word for January is “Janeiro”, as in Rio de Janeiro.


The Costello Tetra can grow to 5 cm (2 inches), long but is usually less than this.  It is an elongated fish, so it is a fairly small one.

Water Conditions

The water the Costello Tetra comes from in the wild is soft and acidic.  This fish can be acclimatised to harder water, up to about 12 degrees of general hardness, and water with a pH of as high as 7.5.  However, it is more sensitive to water chemistry than the Head and Tail Light Tetra and many of its other relatives; I suggest slightly acidic to neutral water, as soft as is practicable.  The water needs to be kept clean.  Avoid rapid changes in the water conditions.

A temperature of between 23 and 27 degrees C (between 73 and 81 degrees F) is suitable. 


The Costello Tetra is an omnivore with a preference for animal food.  In an aquarium it will eat a high protein fish flake readily, but needs some live food like Mosquito larvae or Daphnia if possible.  When live food is not available, frozen food like blood worms or brine shrimp can be used to add variety to your fish’s diet.


The Costello Tetra is a very peaceful schooling fish and a school of 6 or more of these attractive fish makes a good addition to a community tank with other small peaceful fish liking neutral water at about 24 degrees C.


The female is a little plumper than the male.  This difference is greater when she is in breeding condition and is loaded with eggs.  The male has a slightly hooked anal fin.


For breeding, the Costello tetra needs very soft, slightly acidic water of about 25 degrees C (77 degrees F).  They lay their eggs over plants.  Unlike many fish, they are more likely to lay their eggs in the evening after the light fades than the morning.  They are eggs scatterers and lay over plants.

Raising the Fry

The eggs normally hatch in about 24 hours and the babies should be free swimming in another 3 days.  They are small and need infusoria at first.  The water quality in important and will need regular partial water changes with water of the same temperature, acidity and hardness.

Conservation Status

In the UICN Red list the Costello Tetra is a species of least concern with a stable population.

Other Common Names

In France the “Costello Tetra” is called “Néon vert” or “Tétra Costello”.  In Germany it is called “Grüner Neon”, in Denmark, “Costellotetra” or “Grøn neon”; in Poland, “Zwinnik” or “zielony”; in Peru, “Mojarita” or “Enero tetra”; in Sweden, “Costellotetra”; and in Chinese it is called “豚形半線脂鯉”, “豚形半线脂鲤” or “金线黑灯、一月灯”.

In English the three common names used are “Costello Tetra”, “January Tetra” and “Green Neon”.  The name Green Neon is quite misleading because this is the common name of “Paracheirodon simulans” which is quite different in appearance from “Hemigrammus Hyanuary”.

The common names in several of the other languages also mean “Green Neon” Some of them are clear equivalents of Costello Tetra.  Only Peru and China uses a translation of January in one of their names for this fish.


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Costello Tetra
By Thomas Gräfe, Schönheide (Thomnight) (self-made, eigenes Werk) [CC-BY-SA-2.0-de (], via Wikimedia Commons
Female Costello Tetra