January tetra

Geographic Origin and Biotope: Amazon River basin, especially near Lake Hyanuary (hence the name). Populates flooded forests and calm lowland basins rich in submerged obstacles and vegetation.

Taxonomy and Morphology: Costello Tetra / Green Neon Tetra (Hemigrammus hyanuary). Small cyprinid with a lozenge profile, slightly "taller" than its cousins. It has the typical black spot of the genus Hemigrammus located on the root of the tail.

Social Behavior: Gregarious (needs 6 to 10 individuals) and shy. In bare tanks it is prone to panic attacks; actively explores only if it feels shielded by nearby plant beds (edge effect).

Coloration and Sexual Dimorphism: Underrated: olive/golden body crossed by a bright golden/green horizontal line that ends in the caudal peduncle with a sharp black "eye" bordered with upper yellow-gold. Females noticeably swollen on the abdomen.

Aquarium Setup: The emblem of the planted aquarium fish. Color contrast is obtained only by offering densely planted backgrounds or the shade of a large Anubias/Echinodorus, using dark backgrounds and non-turbulent waters.

Diet and Feeding: Surface insectivore and omnivore. Equipped with a slightly upward-facing mouth, preys on springtails, mosquitoes and in the aquarium attacks slow-sinking flakes. Never let them lack freeze-dried brine shrimp (rich in carotenes).

Water Quality: Strong tolerance to neutral ranges. Resists very well to GH hardness close to 10 or 12, as long as it does not suffer sudden temperature increases over 28 degrees (82°F), where it suffers from lack of oxygen.

Compatibility and Tankmates: Perfect for Dutch aquariums in community with delicate fish (Microdevario, small Badis, Corydoras pygmaeus). Discard explosive cohabitations like Clown Loaches or large barbs that would cause lethal fading in the Costello Tetra.

Aquarium Reproduction: Lays eggs in pairs (although not monogamous) in the half-light of the moss at dawn, tiny eggs (Egg scatterer). Requires darkness and very pure water to avoid fungal attacks on the laid caviar.

Risks and Diseases: Rarely available fish, unfortunately replaced in community tanks by more "commercial" species. Suffers from white spot disease (Ich) following drastic temperature changes.