Glowlight Tetra (Hemigrammus erythrozonus) is a small, hardy characin instantly recognizable by the vivid iridescent orange-red stripe running from snout to tail along an otherwise translucent silvery body. First introduced to the hobby in the early 1930s, it remains a classic community fish nearly a century later thanks to its easy care, peaceful nature, and constant gentle activity in a school.
Native to the Essequibo River basin in Guyana (including the Mazaruni and Potaro tributaries), where it inhabits slow, shaded blackwater creeks stained brown by tannins from decaying leaf litter. The water here is naturally soft and acidic — replicating this with dark substrate, driftwood, and a touch of leaf litter or botanicals brings out the deepest, most vivid coloration in the stripe.
Feeding & Care Tip: Glowlights are micropredators that thrive on a varied diet — use a high-quality micro-pellet or flake as the daily staple, and feed small portions 1–2× daily rather than one large meal to protect water quality. For best color and condition, supplement 2–3× weekly with frozen or freeze-dried baby brine shrimp, daphnia, or finely chopped bloodworms — these mirror their natural diet far more closely than dry food alone and are genuinely necessary for ideal coloration, not just a treat.
Keep in a proper shoal of 8–10 or more — a small group will stay skittish and hide, while a full school displays the natural midwater schooling behavior this fish is known for. They are peaceful and mix well with other small tetras, guppies, platies, mollies, Corydoras, and smaller gouramis. Avoid larger or boisterous tankmates, including angelfish, which may see a Glowlight as a meal.
A well-planted tank with floating cover to diffuse light suits this species best — bright, harshly lit tanks wash out the stripe's color and stress a naturally shade-loving fish. Stable water quality matters more than chasing an exact number; sudden swings in pH or temperature are far harder on this species than a slightly imperfect but steady parameter.
| Difficulty | Beginner — Easy |
| Temperament | Peaceful — Community |
| Typical Adult Size | 1.5–2 inches (4–5 cm) |
| Min. Group Size | 8–10 minimum for confident schooling |
| Ideal Temp | 74–80°F (23–27°C) |
| Ideal pH | 5.5–7.0, soft and slightly acidic for best color |
| Ideal GH | 1–8 dGH |
| Staple Food | High-quality micro-pellets or flake |
| Treat / Supplement | Frozen/freeze-dried baby brine shrimp, daphnia, chopped bloodworms — 2–3× weekly for ideal color and condition |
| Origin | Essequibo River basin, Guyana — blackwater tributaries |
| Notes | Dark substrate and dim/diffused lighting bring out the iridescent stripe. Avoid bright, harsh lighting. Sensitive to sudden parameter swings — stability matters most. |
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