Glowlight Tetra
Hemigrammus erythrozonus
Min Tank Size
40L
Adult Size
4 cm
Lifespan
4 years
School Size
6+
About
Native to the Essequibo River basin in Guyana, glowlight tetras are one of those fish that look almost fake under good lighting. The body is translucent with a faint golden sheen, and running from nose to tail is a vivid orange-red stripe that genuinely appears to glow in a well-lit planted tank. Compared to neon or cardinal tetras, they don't get nearly as much attention, which is a shame because they're arguably easier to keep and just as striking in a proper setup.
They do best in soft, slightly acidic water that mimics their natural blackwater habitat, somewhere around pH 6.0 to 7.0 and temperatures between 24 and 27 degrees. They're tolerant enough that slightly harder or more neutral water won't kill them, but you'll notice the colors deepen significantly in softer, tannin-stained conditions. Adding Indian almond leaves or driftwood makes a real difference.
Diet is simple: they accept flake food without fuss, but mixing in frozen daphnia, microworms, or cyclops keeps them healthy and enhances coloration over time.
Behaviorally, glowlights are about as peaceful as tetras get. They school tightly when kept in good numbers, spend most of their time cruising the midwater, and never bother anything they can't eat.
A group of eight or more in a planted 60-liter tank with dark substrate and soft lighting is genuinely one of the most calming aquarium setups you can build. They reward patience and attention to water chemistry more than most beginner fish do.
Water Parameters
Temperature
°CpH
GH
dGHKH
dKHSwimming Level
Flow Preference
Keeping multiple Glowlight Tetra together
Glowlight Tetra are shoaling fish and need company of their own kind. Keep a group of at least 6. Smaller groups leave them stressed, washed-out in color, and prone to hiding.
Compatibility
These are excellent community fish for smaller tanks. They pair well with other peaceful South American species like rummy nose tetras, ember tetras, corydoras, dwarf cichlids such as apistogrammas (in larger tanks with plenty of cover), and small rasboras. Avoid anything large enough to swallow them whole, which includes many medium cichlids, large gouramis, and angelfish once grown. Betta compatibility is situational and depends heavily on the individual betta. With dwarf shrimp, adults are usually fine but shrimp fry may get picked off. A classic and reliable combo is glowlights with pygmy corydoras and a small group of otocinclus.
Commonly kept with
Species this one is most often paired withCommonly tried but avoid
Often paired, but shouldn't beCare Notes
The most common mistake is keeping too few. A group of three or four looks fine in the store but results in dull, stressed fish that hide constantly. Go to at least six, ideally eight or more. The second mistake is ignoring water hardness. They survive in harder water but the stripe fades noticeably and they never look their best. Soft water with some tannins makes a huge difference to color. Feed a varied diet rather than flakes alone, and do consistent small water changes rather than infrequent large ones. They're sensitive to sudden parameter swings even if they tolerate a wide range overall.
Behavior & Aggression
Glowlight tetras are not aggressive fish. There's no meaningful conspecific aggression, no fin nipping, and no territorial behavior worth mentioning. The only time behavior becomes an issue is when the group is too small. Under six fish, they get skittish, spend more time hiding, and occasionally show mild chasing within the group as a stress response. Keep a proper school and this disappears entirely. They're one of the safest tetras you can put in a mixed community.
Things to Know
- Small enough to be eaten by medium-large predators, choose tankmates carefully.
- May pick at very small shrimp or shrimp fry despite being generally peaceful.
- School size below 6 leads to skittish, stressed behavior and faded coloration.
- Can be shy and wash out in very bright, open tanks.
- A tight fitting lid is recommended as they can jump.
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