Costae Tetra (Hemigrammus hyanuary)
Also known as: Hyanuary Tetra, Costae Hyanuary Tetra
 
The Costae Tetra is a peaceful and somewhat underrated South American tetra with a distinctive reflective silver body and a subtle dark lateral line. Under good lighting, the flanks show green–gold iridescence, and males may display mild reddish tones near the tail. It’s an active schooling species that thrives in planted aquariums and soft, acidic water.
 
Care Sheet
Scientific Name
Hemigrammus hyanuary
Adult Size
3.5–4 cm (1.5 inches)
Lifespan
3–5 years
 
Temperament
Peaceful, social, fast-moving
Best kept in groups of 8+ (ideally 12+ for best behaviour and schooling)
 
Tank Size
Minimum 40 L (10 gallons)
Best kept in 60–80 L for proper schooling and tank mates
 
Water Parameters
Typical Amazonian softwater species:
Temperature: 23–28°C
pH: 5.0–7.2
Hardness: Soft (1–10 dGH)
Flow: Gentle
Environment: Clean, well-oxygenated water
Blackwater or tannin-rich conditions enhance their colouration.
 
Diet
Omnivorous micro-predators
Offer:
High-quality micro-pellets or flakes
Frozen foods (daphnia, brine shrimp, bloodworms)
Live foods (baby brine, grindal worms)
Occasional vegetable-based flakes for balance
 
Tank Setup
Substrate: Sand or fine dark substrate to bring out colour
Plants: Dense planting + open mid-water space
Hardscape: Driftwood, leaf litter, roots
Lighting: Low to medium (they show better colour under softer light)
Background: Dark backgrounds make them look more vivid
 
Behaviour
Peaceful, excellent community fish
Displays natural schooling behaviour in groups
Good tankmates:
Small tetras
Rasboras
Pencilfish
Corydoras
Dwarf apistos (non-aggressive species)
Otocinclus
Avoid large or fin-nipping species.
 
Breeding
Moderately difficult egg scatterer:
Use a separate breeding tank with fine-leaved plants or a mesh bottom
Soft, acidic water (pH 5.0–6.2)
Condition adults with live foods
Remove adults after spawning
Eggs hatch in ~24 hours; fry need infusoria, then baby brine shrimp