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Glowlight Tetra
Hemigrammus erythrozonus
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Photo by Tetra_Glowlight.jpg: gonzalovalenzuela derivative work: Kyknos (talk) · CC BY 2.0
Passport
- Family
- Tetras
- Grows to
- 4 cm (1.6")
- Lives
- 4–5 years
- Temperament
- Peaceful
- Care
- Beginner
- Swims
- Mid-water
- Keep
- In a group of 6 or more
- Water
- 24–28 °C (75–82 °F)
Guyana
Care requirements
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On record for Glowlight Tetra: adult size, lifespan, minimum tank, temperature, ph, hardness, minimum group, diet, care level, swim level, tank length.
A figure that is not on record is left out rather than guessed. One marked Suggested comes from keeping knowledge rather than a page.
- Minimum tank 70 L / 18.5 US gal
- pH 5.5–7.5
- Hardness 2–15 dGH
- Diet omnivore
- Tank length 60 cm minimum
Care notes written from general aquarium knowledge, not from the cited sources.
About
Glowlights do one thing and do it beautifully: a single orange-red line runs from nose to tail through a body that's otherwise almost transparent. Lit from the front it looks like a filament switched on inside the fish.
They're one of the best tetras for an ordinary community tank, and that's not faint praise. Lively without being pushy, colourful without needing a specialist setup, and peaceful with everything that isn't big enough to eat them.
They come from forest tributaries of the Essequibo in Guyana, where the water is stained dark with tannins. Commercial breeding has made them adaptable enough that you don't have to reproduce any of that, though they look better if you nod toward it.
Tank setup
Plant your glowlights a proper tank and they'll pay you back. In a bare setup they look washed out and thin, and people conclude the fish is dull when what's dull is the arrangement around it.
Use a dark substrate and moderate light. The orange line reads as bright only against something darker, and under a hard white lamp over pale gravel it barely registers.
Add wood and a few dried leaves if you want the full effect. Tannins tint the water, drop the light further, and bring the colour up noticeably.
They're genuinely happy in acidic water and merely tolerant of alkaline, so if your tap runs hard expect a slightly quieter fish rather than a sick one.
Feeding
Glowlights are among the easiest tetras to feed. They take flake, granules and anything else offered without hesitation, and they'll come up for it.
Feed live and frozen food regularly anyway, because condition and colour both answer it quickly. Daphnia, bloodworm and brine shrimp are the usual and all work.
Match the size to the mouth. It's a small fish and a large granule just gets nudged around the tank.
Avoid: relying on dried food alone. They'll live on it and they won't look like the fish in the photograph.
Filtration and flow
Gentle to moderate flow is right. Glowlights come from slow forest streams and won't thank you for a strong current, though they cope better than the really delicate blackwater tetras.
Filter for the waste and keep up with water changes. They're hardy, and the hardiness is what lets people get away with poor maintenance until the colour goes.
Peat filtration or botanicals soften the water and suit them if you want to go that way. Neither is necessary.
With plants
Glowlights are completely safe with plants and belong in a densely planted tank. Nothing is eaten, dug or damaged.
Plant the back and sides and keep an open lane through the middle. They're active swimmers that want somewhere to run and cover to duck into, and a tank offering both keeps them out where you can see them.
Fine-leaved plants and moss are worth including if you'd ever like fry to appear on their own.
Health
They're hardy and forgiving, and most keepers never have a problem with them. Ich after a temperature swing is the usual complaint, as with any small shoaling fish.
Watch the line rather than the body. A glowlight whose stripe has gone dull and stayed dull is telling you the water has drifted, well before anything else in the tank shows it.
Quarantine new arrivals if you can. They're bred in huge numbers and shipped a long way, and what arrives with them is more of a risk than anything the species suffers from on its own.
Breeding
Glowlights are an easy tetra to breed, which makes them a good first attempt. They scatter adhesive eggs among fine-leaved plants and then hunt them down.
Set up a dim separate tank with moss, spawning mops or a mesh floor, and use soft acidic water — this is the one place where hitting the soft end really matters, because the eggs won't develop otherwise. Condition the adults on live food first.
Take the adults out as soon as eggs appear. Keep the tank shaded while they develop, start the fry on infusoria, and move to baby brine shrimp once they can handle it.
Tank mates
Avoid9
- Convict Cichlid Convict Cichlid grows to 15 cm against Glowlight Tetra at 4 cm, big enough to eat it.
- Jewel Cichlid Jewel Cichlid grows to 15 cm against Glowlight Tetra at 4 cm, big enough to eat it.
- Pictus Catfish Pictus Catfish grows to 12 cm against Glowlight Tetra at 4 cm, big enough to eat it.
- Common Goldfish Common Goldfish is not safe with Glowlight Tetra: common goldfish and tetras are a bad pairing.
- Demasoni Cichlid Demasoni Cichlid is not safe with Glowlight Tetra: african cichlids and tetras are a bad pairing.
Only with care10
- Chinese Algae Eater Chinese Algae Eater is aggressive and Glowlight Tetra is peaceful.
- Cherry Barb Glowlight Tetra and Cherry Barb are an uneasy mix: barbs and tetras are a pairing to watch.
- Gold Barb Gold Barb is a risk to Glowlight Tetra: barbs and tetras are a pairing to watch.
- Odessa Barb Glowlight Tetra and Odessa Barb are an uneasy mix: barbs and tetras are a pairing to watch.
- Paradise Fish Paradise Fish is a risk to Glowlight Tetra: large gouramis and tetras are a pairing to watch.
No conflict is recorded with the other 85 species in the database, so nothing to flag. 4 species are not covered at all, so they could not be judged either way.