Green Neon Tetra
Paracheirodon simulans
Min Tank Size
40L
Adult Size
2.5 cm
Lifespan
3 years
School Size
8+
About
Hailing from the upper Rio Negro and surrounding blackwater tributaries in South America, the green neon tetra is the smallest of the three neon-style species and arguably the most striking when kept in conditions that actually suit it. At just 2.5 cm fully grown, these fish disappear into a jewel-like flash of turquoise-blue and green as they catch the light, with far less red on the body than a standard neon tetra. That iridescent stripe practically glows in a dimly lit blackwater setup over dark substrate.
They're genuinely soft-water specialists. pH between 4.0 and 6.5, very low hardness, warm temperatures around 26 to 28 degrees, and tannin-stained water isn't just a preference for them, it's close to a requirement if you want healthy, long-lived fish. Most losses happen because hobbyists try to keep them in neutral or slightly hard tap water and wonder why they fade and die within months. Get the water right and they're surprisingly resilient.
Feeding is easy. They'll take quality micro-sized flake, crushed flake, micro pellets, and relish small live or frozen foods like baby brine shrimp, micro worms, and daphnia. A varied diet keeps their colors at their best.
Behaviorally they're completely peaceful, spending most of their time schooling tightly in the mid-water column, especially in open areas between plants. Most fish available in the hobby are wild-caught, which means careful quarantine is smart before adding them to an established tank. Their small size also demands careful thought about tankmates.
Browse real blackwater builds featuring these fish and you'll quickly see why they're a centerpiece choice, not an afterthought.
Water Parameters
Temperature
°CpH
GH
dGHKH
dKHSwimming Level
Flow Preference
Keeping multiple Green Neon Tetra together
Green Neon Tetra are shoaling fish and need company of their own kind. Keep a group of at least 8. Smaller groups leave them stressed, washed-out in color, and prone to hiding.
Compatibility
Their tiny size is the main compatibility issue. Any fish with a mouth large enough to swallow a 2.5 cm fish is a bad neighbor, including many popular community species like gouramis, angelfish, and even larger tetras. Best tankmates are similarly sized nano fish: ember tetras, chili rasboras, pygmy corydoras, and small pencilfish all share the blackwater preference and won't threaten them. Dwarf shrimp like neocaridina can coexist but adult green neons will eat shrimplets, so breeding colonies may suffer. Celestial pearl danios and boraras species are also compatible choices. Avoid anything nippy, fast, or considerably larger.
Commonly kept with
Species this one is most often paired withCommonly tried but avoid
Often paired, but shouldn't beCare Notes
The single biggest mistake is keeping them in standard tap water. They need genuinely soft, acidic, warm conditions, not just 'low-ish pH.' Most tap water is too hard for long-term success. Using RO water remineralized to very low GH, or collecting natural rainwater and treating appropriately, is often necessary. A heavily planted tank with botanicals, leaf litter, and driftwood helps replicate blackwater chemistry and keeps them comfortable. Quarantine is essential for wild-caught specimens before introducing them to any established system.
Behavior & Aggression
Green neon tetras have essentially no aggressive behavior to speak of. They don't fin nip, don't claim territory, and don't squabble meaningfully with conspecifics. The only real behavioral concern is that a school kept too small, fewer than eight fish, may become skittish and hide constantly rather than shoal openly in the midwater. That stress isn't aggression outward, it's anxiety inward. Keep a decent group and they'll be relaxed and visible.
Things to Know
- Wild-caught specimens are common and may need a quarantine period to settle.
- Requires very soft, acidic water. Hard tap water causes rapid decline.
- Tiny size makes them vulnerable to larger tankmates that may eat them.
- Will not thrive or show full color outside of blackwater-style conditions.
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