Glowlight tetra - Hemigrammus erythrozonus

Scientific name: Hemigrammus erythrozonus

Common name: Glowlight tetra

Family: Characidae

Usual size in fish tanks: 4 - 5 cm (1.57 - 1.97 inch)

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Recommended pH range: 5.5 - 7

Recommended water hardness: 1 - 8°N (17.86 - 142.86ppm)

0°C 32°F30°C 86°F

Recommended temperature range: 23 - 27 °C (73.4 - 80.6°F)

The way how these fish reproduce: Spawning

Where the species comes from: South America

Temperament to its own species: peaceful

Temperament toward other fish species: peaceful

Usual place in the tank: Middle levels

General Information

The Glowlight tetra (Hemigrammus erythrozonus) is a small, peaceful characin native to the Essequibo River drainage (Guyana), where it inhabits slow, shaded blackwater creeks rich in leaf litter and tannins. A vivid copper–orange “glow” runs from the snout through the lateral line to the tail. Adult size is typically 4–5 cm (1.6–2.0″). Keep in a proper shoal of 8–10 to reduce skittishness and show natural schooling.

Food & Feeding

Omnivorous micro-predator. Use quality micro-flakes or small sinking granules as the staple, with frequent small portions of frozen/live foods such as baby brine shrimp, daphnia, cyclops, and finely chopped bloodworms. They may graze a little biofilm/algae, but animal protein and varied micro-foods keep color and condition. Feed small amounts 1–2× daily to protect water quality.

Sexing

External differences are subtle: females are fuller-bodied, especially when gravid; males are slimmer and may show slightly sharper stripe contrast. Color is otherwise similar in both sexes.

Breeding

An egg-scattering tetra whose eggs are light-sensitive. Use a small, dim breeding tank with very soft, acidic water (see below), spawning mops or fine plants, and near-darkness. Condition a pair or small group on live/frozen foods. Remove adults post-spawn. Eggs typically hatch in ~24–36 hours; fry become free-swimming a few days later. Start with infusoria/liquid fry foods, then freshly hatched brine shrimp as they grow.

Lifespan

Commonly 3–5 years with good water quality and low stress (occasionally longer).

Tank Requirements & Water Parameters

Tank size: a long 60 cm/24″ tank for a group; larger volumes stabilize water.
Water: aim for soft, acidic conditions: pH ~5.5–7.0 (blackwater at the lower end), hardness ~1–8 °dH, temperature 23–27 °C (73–81 °F). Keep nitrate very low.
Filtration & flow: gentle flow with high oxygen. Dark substrate, driftwood, and botanicals (almond leaves) help provide tannins and shade; floating plants diffuse light.
Maintenance: small, frequent water changes; avoid abrupt parameter swings.

Compatibility & Tank Mates

Peaceful shoaler. Ideal with other small, calm community fishes that enjoy similar soft water (small rasboras, pencils, peaceful dwarf cichlids like Apistogramma, small Corydoras). Avoid large/boisterous species and notorious fin-nippers.

Behaviour & Usual Place in the Tank

Occupies the mid-water to upper-mid levels, schooling in open lanes and dipping into cover when startled.

Short Description

Glowlight tetras are gentle, copper-striped characins from Guyana’s blackwater streams. Keep them in groups in soft, acidic, dimly lit aquaria with fine, varied foods to see tight schooling and strong color.

Q&A

Where are they from? The Essequibo drainage (Guyana), in slow, tannin-stained blackwater creeks.
How many should I keep? 8–10 to reduce stress and promote schooling.
Can I breed them? Yes, but it’s easier in very soft, acidic water and darkness; eggs are photo-sensitive.
Do they eat plants? They generally don’t damage plants; they may pick at biofilm on leaves.