Glowlight Tetra

Also known as: Hemigrammus erythrozonus

The Glowlight Tetra (Hemigrammus erythrozonus) is a small, peaceful freshwater fish native to the blackwater streams of the Amazon Basin. The Glowlight Tetra originates from Amazon River basin in Guyana, Suriname, and French Guiana, reaches 4.5 cm in captivity, typically lives 5, and is kept at 24C (75F). Individual fish vary, so treat this as a general guide rather than a guarantee.

Species at a glance

Origin: Amazon River basin in Guyana, Suriname, and French Guiana
Adult size: 4.5 cm (1.8 in)
Life span: 5
Temperament: Peaceful and schooling
Tank size: 40 L (10 gal)
Water temp: 24C (75F)
pH range: pH 5.5-7.5
Diet: Omnivorous; accepts high-quality flakes, micro pellets, and live/frozen foods such as brine shrimp, daphnia, and bloodworms
Other names: Hemigrammus erythrozonus

About the Glowlight Tetra

The Glowlight Tetra (Hemigrammus erythrozonus) is a small, peaceful freshwater fish native to the blackwater streams of the Amazon Basin. It is named for its distinctive iridescent orange-red stripe that runs horizontally along its body, resembling a glowing filament. This species thrives in soft, slightly acidic water and is best kept in groups of six or more to exhibit natural schooling behavior. Its hardy nature and striking appearance make it a popular choice for community aquariums.

Lifespan and health

With proper care, Glowlight Tetras typically live 4–6 years in captivity, with exceptional specimens reaching up to 8 years under optimal conditions. Lifespan is heavily influenced by water quality, diet consistency, and stress levels—fish kept in unstable parameters, overcrowded tanks, or with inadequate nutrition often show shortened lifespans of 2–3 years. Regular monitoring of ammonia, nitrite, and nitrate levels, along with consistent temperature and pH, is crucial for longevity. Avoid sudden water changes; acclimate new fish slowly over 1–2 hours using the drip method to prevent osmotic shock. Common health issues include ich (white spot disease), often triggered by stress or temperature fluctuations—treat with gradual temperature increase to 28°C (82°F) and appropriate medication if needed. Fin rot can occur due to poor water quality or aggression from tankmates; maintain pristine conditions and remove aggressive individuals. Internal parasites, such as nematodes, may cause wasting despite normal appetite—quarantine new fish and consider prophylactic treatment with medicated food if symptoms appear. Columnaris (cotton wool disease) is rare but possible in warm, dirty water; immediate isolation and antibacterial treatment are required. Preventative care—consistent water changes, varied diet, and low-stress environment—reduces disease incidence by over 80%.

Overview

Care and tank setup

For optimal care, maintain a minimum tank size of 40 liters (10 gallons) for a school of 6–8 Glowlight Tetras, though larger tanks (60+ liters / 15+ gallons) are recommended for better stability and swimming space. Use a dark substrate and provide dense planting with live plants like Java moss, Amazon sword, or floating vegetation to mimic their natural blackwater habitat and reduce stress. Gentle filtration is essential—avoid strong currents; a sponge filter or low-flow hang-on-back filter is ideal. Keep water temperature stable between 24–26°C (75–79°F) and pH between 5.5–7.0, with hardness below 10 dGH. Perform weekly 20% water changes to maintain low nitrate levels (<20 ppm). Feed small amounts 2–3 times daily, offering only what they can consume in under 2 minutes to prevent overfeeding and water quality issues. A varied diet including high-quality micro pellets, crushed flakes, and 2–3 weekly feedings of live or frozen foods like baby brine shrimp or daphnia enhances coloration and health. Avoid large or aggressive tankmates; ideal companions include other peaceful tetras (e.g., Neon, Cardinal, Ember), Corydoras catfish, small rasboras, and dwarf shrimp. Never house with fin-nippers like Tiger Barbs or large cichlids. Tankmates should be selected carefully to avoid competition for food or space. Glowlight Tetras are timid and may hide if kept with boisterous or aggressive species. A group of at least 6 individuals is critical for their well-being—solitary or paired fish often become stressed, lose color, and may refuse to eat. Ensure the tank has shaded areas and hiding spots using driftwood or leaf litter (e.g., Indian almond leaves) to replicate their natural tannin-stained environment and promote natural behavior.

Adding a Glowlight Tetra? Research the species’ adult size and temperament carefully, quarantine new fish before introducing them to your tank, and buy from reputable aquarium stores or breeders.

Breed information on this page is based on the Wikipedia article on the Glowlight Tetra, supplemented with additional research. Reviewed for accuracy.