Green neon tetra - Paracheirodon simulans

Scientific name: Paracheirodon simulans

Common name: Green neon tetra

Family: Characidae

Usual size in fish tanks: 2 - 3 cm (0.79 - 1.18 inch)

014

Recommended pH range: 5 - 6.5

Recommended water hardness: 0 - 4°N (0 - 71.43ppm)

0°C 32°F30°C 86°F

Recommended temperature range: 24 - 27 °C (75.2 - 80.6°F)

The way how these fish reproduce: Spawning

Where the species comes from: South America

Temperament to its own species: peaceful

Temperament toward other fish species: peaceful

Usual place in the tank: Top levels

General Information

The Green neon tetra (Paracheirodon simulans) is a tiny characin native to the upper Rio Negro and Orinoco basins in South America. It inhabits shaded, slow blackwater creeks (igapó/igarapé) rich in leaf litter and dissolved tannins. Compared with P. innesi and P. axelrodi, it stays smaller and shows a more green-turquoise lateral stripe with much less red on the body. Adult size in aquaria is usually 2–3 cm. Keep in shoals of 10 for natural behavior and confidence./p>

Food & Feeding

Omnivorous micro-predator that picks at tiny invertebrates and biofilm. Use quality micro-flakes or micro-pellets as the staple, and rotate small frozen/live foods (baby brine shrimp, cyclops, daphnia, finely chopped bloodworms). Offer tiny portions 1–2× daily; fine foods prevent choking and reduce waste. A bit of spirulina-based feed helps round out the diet.

Sexing

External differences are subtle. Mature females are rounder/fuller-bodied, especially when gravid; males remain slimmer and may show slightly crisper stripe definition.

Breeding

P. simulans is an egg-scatterer and not easy to spawn. For best results, use a separate, dim tank with very soft, acidic water (see parameters below), spawning mops or fine plants, and near-darkness because the eggs are light-sensitive. Adults may spawn in a small group; remove them post-spawn. Eggs typically hatch in ~24–36 h; once free-swimming, start with infusoria/liquid fry foods, then newly hatched brine shrimp.

Lifespan

Commonly 3–5 years with excellent water quality and low stress.

Tank Requirements & Water Parameters

Group & space: shoal of 10 ; a long 45–60 cm (18–24″) tank with dense plants, leaf litter, and shaded areas.
Water: this is a blackwater specialist. Aim for pH ~5.0–6.5 (can adapt up to neutral if tank-bred and acclimated), GH 0–4 °dH, temperature 24–27 °C (76–81 °F). Keep nitrate very low; stable, soft conditions matter more than chasing exact numbers.
Filtration & flow: gentle flow, high oxygen; use dark substrate, wood, and botanicals for tannins. Floaters help diffuse light.
Maintenance: small, frequent water changes; avoid sudden parameter shifts.

Compatibility & Tank Mates

Peaceful, timid shoaler. Combine with other tiny, non-nippy soft-water species (e.g., small rasboras, dwarf pencils, gentle dwarf corys/aspidoras, small apistogrammas that won’t prey on them). Avoid large or boisterous tankmates and fin-nippers.

Behaviour & Usual Place in the Tank

Occupies the upper to mid-water layers, especially under leaf-litter shade and among fine plants. Provide open lanes for schooling plus dim refuges to reduce skittishness.

Identification Notes

Often confused with neon (P. innesi) and cardinal tetras (P. axelrodi). P. simulans is smaller; the blue-green stripe extends more onto the head/eye and the red coloration is minimal, restricted near the tail.

Short Description

Green neon tetras are miniature blackwater characins from the upper Negro/Orinoco that thrive in large groups, very soft, acidic water, and subdued lighting. Provide tiny varied foods and pristine conditions to see their best color and schooling behavior.

Q&A

Where is it from? Upper Rio Negro and Orinoco basins in South America (blackwater creeks).
Do they tolerate neutral water? Tank-bred lines often adapt to ~pH 7.0 if very clean and stable, but breeding and long-term peak condition are easier in soft, acidic water.
How many should I keep? A group of 10 —bigger shoals reduce stress and bring out schooling and color.
How hard is breeding? Challenging—requires very soft, acidic water, darkness for eggs, and fine starter foods.