Green Neon Tetra Care Guide: The Nano Blackwater Specialist

The green neon tetra (Paracheirodon simulans) is the smallest and least well-known member of the Paracheirodon genus — a trio that includes the wildly popular neon tetra (P. innesi) and cardinal tetra (P. axelrodi). At just 1 inch fully grown, the green neon tetra is a true nano fish, and its brilliant blue-green iridescent stripe — which extends the full length of the body — glows against dark water and green plants in a way that photographs struggle to capture.

Green neon tetras are native to the blackwater tributaries of the upper Rio Negro and Orinoco river basins in South America. Unlike neon tetras, which have been captive-bred in enormous numbers for decades, green neon tetras are mostly wild-caught. This gives them a natural robustness that mass-bred neons often lack, but it also means they are more particular about water chemistry — soft, acidic water brings out their best.

This guide covers everything you need to keep green neon tetras healthy and displaying their most vivid coloration: tank setup, blackwater parameters, diet for their tiny mouths, schooling requirements, compatible tank mates, and how they compare to their more famous relatives.

Green Neon Tetra at a Glance

How Green Neons Differ From Neon and Cardinal Tetras

The three Paracheirodon species each fill a different niche. Understanding the differences helps you pick the right one for your setup.

Green neon tetras are the smallest at 1 inch, have the most prominent blue-green iridescent stripe (extending the full length of the body to the tail), and show minimal red — just a faint reddish patch near the tail. They prefer the softest, most acidic water of the three and look their best in blackwater setups.

Neon tetras are mid-sized at 1.5 inches, display a distinct blue stripe with a vivid red band covering the back half of the body. Decades of captive breeding have made them the most adaptable of the three, tolerating a wide range of water conditions.

Cardinal tetras are the largest at up to 2 inches, with a full-body red stripe from eye to tail that creates the boldest display. Most are wild-caught and prefer warm, soft water.

For a deeper dive into the neon vs cardinal comparison, see our cardinal tetra vs neon tetra guide.

Aquarium Setup

Green neon tetras thrive in planted nano tanks with soft, acidic water and subdued lighting. A 10-gallon tank is the recommended minimum for a school of 8 to 10 fish. If you want a larger school of 15 to 20 — which produces the most impressive display — a 20-gallon tank gives them room to school naturally without overcrowding.

Substrate

Dark substrates bring out the strongest coloration in green neon tetras. On light-colored gravel, they look pale and unremarkable. On dark substrate in tannin-stained water, the blue-green stripe appears to glow.

• Planted tank soil (Fluval Stratum, ADA Amazonia) — the best choice for green neon setups. Naturally lowers pH and softens water, which green neons prefer. Ideal if running a planted tank.
• Black sand — provides strong color contrast and works well for shrimp-safe setups with cherry shrimp.
• Fine dark gravel — a simpler option for setups without live plants.

Plants and Decor

Green neon tetras feel most secure in densely planted tanks with plenty of cover. Fine-leaved plants like Java moss, Cabomba, and Pogostemon stellatus create the kind of dense vegetation these fish naturally inhabit. Driftwood and Indian almond leaves add tannins that tint the water, lower pH, and create the blackwater aesthetic that brings out their best color.

Lighting

Green neon tetras come from heavily shaded blackwater streams and prefer subdued lighting. Bright overhead lights stress them and wash out their coloration. Floating plants are the simplest way to create the diffused, dappled lighting these fish thrive in. Under moderate lighting against dark water, their blue-green stripe has a vivid, electric quality that bright lights cannot produce.

Filtration

Green neon tetras need gentle flow. At just 1 inch, they are easily pushed around by strong currents. A sponge filter is the ideal choice — it provides gentle biological filtration with minimal current and eliminates the risk of tiny fish being pulled into filter intakes.

If you use a hang-on-back or canister filter, cover the intake with a pre-filter sponge. This is not optional with fish this small. Adjust the flow rate to the lowest comfortable setting.

Water Parameters

Water chemistry is where green neon tetra care becomes more specific than many common community fish. Green neon tetras originate from some of the softest, most acidic freshwater on earth — the blackwater tributaries of the upper Rio Negro, where pH can drop below 5.0 and hardness is near zero.

Temperature

Aim for 75-80°F (24-27°C). The full tolerance range is 74 to 82°F (23 to 28°C).

• 74-75°F — Lower end. Tolerated but not ideal for long-term color and activity.
• 75-80°F — Comfortable range where green neon tetras display their best coloration.
• 80-82°F — Upper end. Increases metabolism and may shorten lifespan over extended periods.

An adjustable heater is essential for maintaining stable temperatures, even in warm climates where nighttime drops can occur.

pH and Hardness

Target pH 5.0-7.0 and hardness under 8 dGH. Green neon tetras are more particular about water softness than neon or cardinal tetras.

• pH 5.0-6.0 — Closest to their natural habitat. Wild-caught green neons display their most vivid coloration in this range.
• pH 6.0-7.0 — Well-tolerated, especially by fish that have spent time acclimating in a dealer’s tanks.
• Hardness 1-8 dGH — Soft water is strongly preferred. Avoid hard water above 10 dGH.

Water Quality

Keep ammonia and nitrite at 0 ppm at all times and nitrate below 20 ppm. Green neon tetras are sensitive to dissolved waste, and poor water quality causes rapid color fading and increased disease susceptibility.

Perform 20% water changes weekly. In smaller tanks under 15 gallons, consider twice-weekly water changes since parameters shift faster in low-volume setups. Always match the temperature of replacement water to the tank — even a 2 to 3°F difference can stress fish this small.

Diet

Green neon tetras are omnivores with tiny mouths. In the wild, they feed on small invertebrates, zooplankton, and plant matter. Their size means food needs to be small enough for them to eat comfortably — large pellets and unground flakes will just be ignored.

What to Feed

How Often to Feed

Feed green neon tetras once or twice per day in small amounts they finish within 60 to 90 seconds. Their stomachs are tiny, and overfeeding is one of the most common mistakes with nano fish. Uneaten food decomposes quickly in small tanks and spikes ammonia — exactly the kind of water quality problem these sensitive fish cannot tolerate.

Schooling Behavior

Green neon tetras are a shoaling species that naturally gather in large groups in the blackwater streams of the upper Rio Negro. They are shy, small fish that rely on group numbers for security — and they show it.

School Size

Keep a minimum of 8 to 10 green neon tetras, though groups of 12 to 20 produce dramatically better results. In smaller groups, green neon tetras hide constantly, stay pale, and rarely venture into the open. In groups of 15 or more, they form flowing, tight schools that move through the planted areas of the tank with visible confidence.

Green neon tetras school more tightly than regular neon tetras and more loosely than rummy-nose tetras. Their schooling behavior intensifies when they feel any perceived threat — a larger fish swimming nearby, movement outside the tank, or a water change — and relaxes during calm periods into a loose, drifting cluster.

Temperament

Green neon tetras are extremely peaceful. They show no aggression toward tank mates and are not fin nippers. They occupy the mid-water column, spending most of their time swimming between the substrate and the surface. Males may occasionally display to each other with brief, harmless fin-flaring, but these interactions are subtle and short-lived.

Compatible Tank Mates

Green neon tetras are excellent community fish for nano and small tank setups, but their tiny size limits which species they can safely live with. Any fish large enough to fit a green neon tetra in its mouth is a potential predator.

Good Tank Mates

Green neon tetras pair particularly well with cherry shrimp. At 1 inch, their mouths are physically too small to eat adult cherry shrimp, making them one of the safest fish choices for a shrimp tank. Dense plant cover provides enough shelter for shrimplets to survive and grow. Many shrimp keepers specifically choose green neon tetras as their tank fish for this reason.

Species to Avoid

Why Are My Green Neon Tetras Pale?

If it happens when the lights first come on, it’s normal. Green neon tetras fade their coloration while resting. Full color returns within minutes.

If the blue-green stripe stays dull during the day:

• Water too hard or alkaline — Green neon tetras display their best color in soft, acidic water (pH 5.0-6.5, under 8 dGH). In hard, alkaline water, they often look permanently washed out.
• No tannins — Adding Indian almond leaves, alder cones, or blackwater extract darkens the water and dramatically enhances their iridescence.
• School too small — Fish in groups under 8 are chronically stressed and fade as a result.
• Substrate too light — Light-colored gravel or bare-bottom tanks cause fish to pale. Dark substrates trigger natural pigment intensification.
• Diet — A dry-food-only diet dulls coloration. Add frozen baby brine shrimp and daphnia for carotenoid pigments.
• Lighting too bright — Harsh overhead light washes out iridescent coloration. Add floating plants.

The best-looking green neon tetra tanks combine dark substrate, tannin-stained water, floating plants, and a school of 12 or more. Get those four things right, and the blue-green stripe will glow.

Common Health Issues

Green neon tetras are hardy fish once established in a suitable environment. Their wild-caught origins give them stronger immune systems than mass-bred species, but they are still susceptible to common aquarium diseases — especially during the stress of acclimation and in poor water quality.

Ich (White Spot Disease)

Ich presents as small white dots on the body and fins. Green neon tetras are susceptible to ich after temperature swings or transport stress. Treatment involves gradually raising the water temperature to 82°F over 48 hours while using an ich medication. Reduce medication dosage by 25 to 50% compared to the standard recommendation, as fish this small can be sensitive to full-strength treatments. Remove activated carbon from the filter during treatment.

Fin Rot

Fin rot appears as frayed or receding fin edges and is almost always caused by poor water quality. Improving tank maintenance with more frequent water changes typically resolves mild cases. For persistent fin rot, treat with a broad-spectrum antibacterial at reduced dosage.

Acclimation Stress

Because most green neon tetras are wild-caught, they arrive at fish stores after transport from South America. Newly purchased fish may be pale, shy, and lethargic for the first few days. Drip acclimate them over 1 to 2 hours to gradually adjust them to your water chemistry. Dim the lights for the first 24 to 48 hours and avoid feeding for the first 12 hours. Most green neon tetras settle in and begin displaying full color within 1 to 2 weeks.

Sources

• FishBase — Paracheirodon simulans species profile. Temperature, pH, size, and distribution data.
• SeriouslyFish — Paracheirodon simulans care profile. Tank size, diet, behavior, and breeding notes.
• Wikipedia — Green neon tetra. Taxonomic classification and habitat overview.

Frequently Asked Questions