Green Neon Tetra
Paracheirodon simulans
A hardy, active South American tetra known for its silvery body, dark-edged fins and energetic schooling behaviour.
Difficulty
Beginner
Min tank size
40 L / 10 gal
Temperament
Peaceful
Diet type
Omnivore
Adult size
2.5–3 cm / 1–1.2 in
Lifespan
3–5 years
Water type
Freshwater
Cardinal tetra at a glance
| Scientific name | Paracheirodon simulans |
|---|---|
| Order | Characiformes |
| Family | Characidae |
| Genus | Paracheirodon |
| Origin | Brazil — Rio Negro basin and nearby blackwater habitats |
| Adult size | About 2.5–3 cm (1–1.2 in) |
| Tank size (min) | 40 L / 10 gal for a small school; larger is better |
| Temperature | 23–28 °C (73–82 °F) |
| pH range | 4.0–7.0 |
| Water hardness | Very soft to soft |
| Diet | Omnivore — fine flakes, micro-pellets, frozen and live foods |
| Temperament | Peaceful schooling fish |
| Care level | Beginner |
Overview
The Cardinal tetra (Paracheirodon simulans) is a robust South American characin that has been popular in the aquarium hobby for decades. Its silvery body, darker dorsal and anal fins and warm red accents make it easy to recognise, while its energetic nature gives a community aquarium plenty of movement.
This is a classic nano tetra. It is peaceful enough for a community aquarium, but its active schooling and occasional fin-nipping mean it should be kept with appropriately sized, active tankmates. A proper school and a long aquarium are much more important than keeping it in a small decorative tank.
Cardinal tetra size & lifespan
How big do Green neon tetras get?
Adults usually reach about 4–5 cm (1.6–2 inches). Females can look deeper-bodied than males, especially when mature and carrying eggs.
How long do Green neon tetras live?
In a clean, stable aquarium, Green neon tetras can live around 2–4 years, sometimes longer. A varied omnivore diet, good filtration, regular maintenance and sufficient swimming space are key factors in keeping them healthy over the long term.
Natural habitat & origin
Paracheirodon simulans is native to the upper Amazon and Orinoco drainage systems of northern South America, especially the Rio Negro region of Brazil and parts of Colombia. Wild fish are associated with shallow, shaded blackwater streams, tributaries and flooded forest habitats where leaf litter, submerged roots and dense vegetation provide cover and feeding opportunities.
Aquarium specimens are widely captive-bred. A planted aquarium with open swimming space, moderate current, good oxygenation and stable water conditions provides a suitable captive environment without needing to duplicate every detail of the wild habitat.
Cardinal tetra tank size & requirements
A 10-gallon (38 L) long aquarium is a sensible minimum for a school of Cardinal tetras. The species is active and can reach a substantial size for a tetra, so horizontal swimming room is more useful than extra tank height. A secure lid is recommended because active tetras can jump when startled.
How many Green neon tetras in a 10 or 20 gallon tank?
A 5-gallon aquariums are better reserved for very small groups; a 10-gallon aquarium is a practical minimum for a proper school. In a 10-gallon tank, a group of 6–10 is a reasonable starting point when filtration and maintenance are strong. Larger aquariums are better for larger groups and mixed community stocking.
| 5 gal (19 L) | Possible only for a carefully maintained small school; more swimming room is preferable. |
|---|---|
| 10 gal (38 L) | A practical minimum for about 6–10 Green neon tetras when the aquarium is mature and well maintained. |
| 20 gal (75 L) | Excellent for 10–15 fish with plants and compatible peaceful tankmates. |
| 29 gal (110 L) | A larger school of 15–25 can work well with thoughtful community stocking. |
| 55 gal (208 L) | Ideal for a substantial school and a varied peaceful community. |
Water parameters
| Temperature | 23–28 °C (73–82 °F) |
|---|---|
| pH | 4.0–7.0 |
| Hardness (GH) | Very soft to soft |
| Filtration turnover | Gentle to moderate circulation with good oxygenation |
Use a fine gravel or sand substrate, hardy live plants and an unobstructed swimming lane through the middle of the aquarium. Green neon tetras may nibble tender vegetation, so tougher plants are a safer choice than delicate soft-leaved species. Moderate filtration and good oxygenation suit their active nature.
Not sure how many litres your tank holds? Check it with theaquarium volume calculator.
What do Green neon tetras eat? Diet & feeding
Green neon tetras are small omnivores and micropredators. A quality flake or appropriately sized pellet makes a good daily staple, while frozen or live foods such as daphnia, brine shrimp and bloodworms provide variety and useful enrichment.
Feed small portions once or twice daily and provide only enough food for the school to finish in a few minutes. Because these fish are active and persistent feeders, overfeeding is easy and can quickly contribute to poor water quality.
Cardinal tetra tank mates & compatibility
Keep Green neon tetras in a school of at least six. They are peaceful by nature, but their energetic swimming style makes them a better match for robust, similarly active community fish than for timid nano species.
Are Green neon tetras aggressive? They are not usually aggressive, but individuals may chase one another or nip fins. This behaviour becomes more noticeable in cramped tanks or when they are kept in an undersized group. Spacious aquariums and compatible tankmates are the best prevention.
Good Cardinal tetra tank mates
- Other small, peaceful tetras and characins
- Small peaceful rasboras
- Corydoras and other appropriately sized peaceful bottom dwellers
- Otocinclus in mature aquariums
- Small peaceful dwarf cichlids when water chemistry and temperament are compatible
- Other calm community fish that will not eat or intimidate them
Avoid
- Large predatory fish that can swallow them
- Aggressive or highly territorial cichlids
- Fin-nipping or boisterous species
- Very large gouramis and other fish that may view them as prey
- Freshly hatched fry and tiny shrimp, which may be eaten
How to breed Green neon tetras
Green neon tetras are egg-scattering fish and can spawn readily when adults are healthy and well conditioned. Feed a varied, nutritious diet for several days before moving selected adults to a separate breeding aquarium.
Use fine-leaved plants or a spawning mop to catch the eggs, provide gentle aeration and keep lighting subdued. Remove the adults after spawning because they may eat the eggs. Once the fry hatch, provide suitably tiny first foods and gradually transition them to newly hatched brine shrimp and other larger foods as they grow.
Naming & buyer’s notes
Cardinal tetra is the standard aquarium name for Paracheirodon simulans. When buying, choose active fish with clear eyes, intact fins, good body condition and strong interest in food. Avoid specimens that remain lethargic, have clamped fins or show obvious signs of disease.
A nano tetra
Do not plan for this species like a tiny nano tetra. Its adult size and constant activity make a longer aquarium much more appropriate.
Plant selection
They are generally plant-safe. Dense planting and floating cover can provide useful shade and help the school feel secure.
Buy a group
A school is essential for normal social behaviour. Buying several healthy specimens together is preferable to keeping a single Cardinal tetra as a display fish.
Cardinal tetra FAQ
- How big do Green neon tetras get?
- Green neon tetras usually reach about 2.5–3 cm (1–1.2 inches). Their small size makes them well suited to planted nano and community aquariums.
- How long do Green neon tetras live?
- With stable water, good nutrition and proper care, Green neon tetras commonly live around 3–5 years in captivity.
- How many Green neon tetras should be kept together?
- Keep them in a group of at least six, with larger groups generally producing more confident and natural schooling behaviour.
- What size tank do Green neon tetras need?
- A 10-gallon (38 L) aquarium is a practical minimum for a small school, although a 20-gallon or larger aquarium gives the fish more stable water conditions and swimming space.
- What do Green neon tetras eat?
- They are omnivores that accept fine flakes and micro-pellets. Regularly offer appropriately sized frozen or live foods such as baby brine shrimp, daphnia and other small foods.
- Are Green neon tetras aggressive?
- No. They are generally peaceful schooling fish. Most chasing is social behaviour within the group rather than serious aggression.
- Can Green neon tetras live with shrimp?
- They are generally compatible with adult dwarf shrimp, but they may eat shrimplets and other very small offspring. Dense plants and moss provide useful cover.
- How do you breed Green neon tetras?
- They are egg scatterers. Condition adults with nutritious foods, use a separate dimly lit breeding aquarium with fine plants or a spawning mop, and remove the adults after spawning because they may eat the eggs.