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Costello Tetra

Hemigrammus hyanuary

Freshwater South America Usually captive bred

Often called the January tetra, this hardy characin features an olive-green body adorned with a bright golden-green spot above a black caudal wedge. Active yet non-aggressive, it thrives in typical community aquaria. Keep in a good shoal to encourage confident, open swimming.

Also called: Costello tetra, January tetra.

4.5 cm adult length, drawn to scale. slim body.

Try it in the planner Opens a tank sized to its minimum with 6 fish added.

What it needs

ItemValueBecause
Adult length 4.5 cm Used for the Space check: the tank must be long enough for the fish to turn round.
Smallest tank 70 L, at least 60 cm long estimated The least water and floor length this species is kept in for good, as a single fish or smallest group.
Extra water per added fish 5 L estimated What each further fish adds once the minimum is met.
Waste load Class 1 of 5 estimated How much waste an adult makes against its size. Feeds the Load check.
Temperature 22 to 27 C Stock sharing a tank need overlapping ranges.
pH 6 to 7.5 Compared with tankmates in the Water check.
Hardness GH 3 to 12, KH 1 to 5 Degrees of general and carbonate hardness.
Flow Medium Low-flow fish are stressed in a strong current.
Light Moderate Matched to the lighting class on the needs sheet.
Group size At least 6, ideally 10 Kept alone or in small numbers it hides, fades or turns on tankmates.
Temperament Peaceful Not territorial.
Swims in Middle water Fish that use different levels share a tank more easily.
Lifespan About 4 years A fish is a long commitment.
Experience Suits a first tank A guide to how forgiving the species is of mistakes.

Tags marked estimated are judged from the size and habits of the species rather than measured, so treat them as a sensible default.

Diet and tank layout

Costello Tetra is an omnivore that swims in the middle of the tank. It is safe with plants. Give it some cover.

Tankmates

Works with

No close matches in the data. Check the pair tool.

Depends

Avoid

Compare any two fish on the compatibility page, or print the equipment for a stock on the needs sheet. How this is worked out: the method.