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Glowlight tetra

Hemigrammus erythrozonus

A tetra with a perfectly descriptive name: an iridescent orange-red stripe runs across the entire translucent body from head to tail, glowing like an incandescent filament in dark water — a spectacular effect in Amazonian biotope tanks with tannins. Among the longest-lived tetras (up to 5 years) and easiest to maintain. Prefers soft, acidic water with dim lighting that enhances its natural luminescence. In schools of 8+ on dark substrate with driftwood and dried leaves, the visual effect is exhibition-grade.

Taxonomy
Class:Actinopteri
Order:Characiformes
Family:Characidae
Genus:Hemigrammus
Species:Hemigrammus erythrozonus

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Water Temperature

22 - 28 °C

pH Value

5.5 - 7.5

Water type

Freshwater

Tank level

Middle

Adult size

4 cm

Minimum tank volume

>= 40 L

Minimum group

>= 6

GH

1 - 15 dGH

KH

1 - 7 dKH

TDS

25 - 295 ppm

Conductivity

39 - 461 uS/cm

Species description

Geographical Origin and Habitat: Essequibo River (Guyana). Swims in slow black streams (Blackwater) dense with vegetation and obscured by the dense forest canopy, with bottoms rich in dead leaves.
Taxonomy and Morphology: Glowlight Tetra (Hemigrammus erythrozonus). Small, delicate characin. Torpedo-shaped body, semi-transparent, largely devoid of marked liveries except for a very strong horizontal lateral line.
Social Behavior: Strictly a schooling fish (mandatorily in groups of at least 8-10). Very peaceful, a bit fearful if left in brightly lit tanks or with large fish. Among themselves the males chase each other mildly.
Coloration and Sexual Dimorphism: The glowing lateral line: an intense neon red/orange ray that cuts the fish from nose to tail. Males are slender, females decidedly more rounded (round if full of eggs) but equally bright.

Care, breeding and tankmates

Aquarium Setup: Dim lights! To enhance the neon colors, a tank with a black or dark bottom, floating plants to shield the light, lots of Cryptocorynes and amber water is needed. If the lights are too strong they become transparent and hide.
Diet and Feeding: Undemanding omnivores. Very small flakes, micro-pellets and abundant doses of very small live or frozen food (nauplii, daphnia, cyclops) essential to keep the "glow" alive.
Water Quality: Extremely hardy: they withstand harder pH than other tetras if adapted slowly, but colors explode at pH 6.0-6.5. Well-matured water (cycled filter) is indispensable to avoid fin rot.
Compatibility and Cohabitation: The best friends of almost all dwarf fish. Perfect for "Nano" tanks with Neocaridina shrimp (rarely prey on the young), Otocinclus, Rasboras, Dwarf Gouramis and Apistogramma. Never keep with Angelfish (they will be prey).
Aquarium Breeding: Reproduction accessible to novices. They scatter dozens of micro-eggs among the fine foliage after intense morning courtships ("Egg-scatterers"). They immediately devour the brood if not removed.
Risks and Diseases: Vulnerable to wasting away due to voracious tankmates (e.g. Tiger Barbs, Giant Danios) that steal food and stress the group leading them to starve holed up in a corner.

Geographic Origin and Distribution

Essequibo River (Guyana). Swims in slow black streams (Blackwater) dense with vegetation and obscured by the dense forest canopy, with bottoms rich in dead leaves.

Origin

Tropical oceans and reefsAmazon, Orinoco, and Guianas

Fish profile

Temperament
Aggressive
They are exceptionally peaceful and somewhat shy, requiring a large school of at least six individuals to feel secure. When kept in smaller numbers, they may become stressed, lose their vibrant colors, and hide continuously. A proper schooling environment encourages their natural, confident behaviors and tight grouping dynamics.
Diet
Omnivore
In the wild, they are micro-predators feeding on small insects, worms, and crustaceans. In the aquarium, they readily accept high-quality crushed flakes, micro-pellets, and freeze-dried foods. Supplementing their diet with live or frozen foods like daphnia, baby brine shrimp, and bloodworms will enhance their coloration and vitality.
Sex ratio
School
Keeping a balanced ratio or a slight majority of females is generally recommended to prevent males from constantly harassing a single female. In a large enough school, the sex ratio becomes less critical as aggression is dispersed. A larger group naturally forms a healthy hierarchy, minimizing any stress related to breeding behavior.
Feeding frequency
Twice daily
It is highly recommended to feed them two to three small meals a day rather than one large one. Offering only what they can consume within a couple of minutes ensures minimal food waste and prevents water quality degradation. Frequent, small feedings closely mimic their natural foraging behavior in the wild.
Bioload
Low
These small tetras produce a minimal bioload, making them excellent candidates for smaller or heavily planted aquariums. They do not generate significant amounts of waste compared to larger species, reducing the burden on the filtration system. However, keeping them in large schools will naturally increase the overall waste output, requiring adequate biological filtration.
Flow
Strong
They prefer a moderate to low water flow that simulates the slow-moving tributaries and flooded forest regions of their natural habitat. Strong currents can exhaust these small fish and cause them significant stress over time. Providing areas of still water, particularly near dense vegetation, allows them places to rest comfortably.
Jump risk
No
Reproduction
Oviparous
Breeding these tetras can be challenging as they are egg-scatterers that provide no parental care. They require soft, acidic water and dim lighting to trigger spawning behavior successfully. A separate breeding tank with fine-leaved plants or a spawning mop is necessary, and parents must be removed immediately after laying eggs to prevent predation.
Compatibility & tankmates
Peaceful
This species is incredibly peaceful and thrives in a community setup with other similarly sized, non-aggressive fish. Excellent tank mates include small rasboras, Corydoras catfish, and peaceful dwarf cichlids. They should never be kept with large or aggressive species that might view them as prey or cause them undue stress.
Tank level
Middle
These fish primarily occupy the middle to upper levels of the water column in the aquarium. They are active swimmers that appreciate ample open swimming space combined with areas of dense planting. While they occasionally dart to the surface for food or explore the bottom, they will spend most of their time cruising the midwater.

Window to the official scientific data of the species

Data synced on: 06/15/2026

Scientific Parameters & Models

Trophic level
2.9 ± 0.32 se
Resilience
High (less than 15 months)
Phylogenetic uniqueness (PD50)
0.5
Bayesian Length-Weight
a = 0.01259, b = 3.05
VulnerabilityLow vulnerability (10 / 100)

Image gallery

Licensed images linked to the species or, when marked, to the closest representative taxon.

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Last updated: 06/30/2026
Glowlight tetra (Hemigrammus erythrozonus) Care Guide & Tank Setup | Atlarium