Green neon tetra

Quick facts

Adult size

3 cm

Lifespan

can live up to 5 years

Tank zone

mid

Temperament

peaceful

Difficulty

intermediate

Schooling

recommended 10+ (critical minimum 6, thrives at 20+)

Typically wild-caught

yes - acclimate slowly

Water parameters

Temperature

24–28°C

pH

4.5 to 6.5

Hardness

0 to 5 dGH

Tank requirements

Minimum volume

50 L

Minimum length

45 cm

Flow

low

Lighting

dim preferred

Substrate

any

Driftwood

preferred

Open swimming room

needed

Feeding

Diet: omnivore, feeds primarily at the mid.

Micro pellets, crushed flake, frozen baby brine shrimp, frozen cyclops, frozen daphnia, and live micro-foods (baby brine shrimp, microworms, daphnia). The mouth is very small, even for a nano tetra. Standard-sized flake needs to be finely crushed. They feed in the midwater column and pick at floating particles. In community tanks, they're easily outcompeted by anything larger or faster. Targeted feeding near their schooling area helps. Feed twice daily in very small amounts. Live food brings out the best coloring.

Compatibility

• Extremely peaceful and tiny. At 2–2.5 cm, green neons are smaller than both neon tetras and cardinal tetras. They belong in nano setups or carefully curated community tanks.
• Best with other small, calm species: ember tetras, chili rasboras, pygmy corys, otocinclus, and shrimp. Any fish large enough to eat them will.
• Groups of 10+ are the minimum for proper schooling and color display. The neon-green stripe along the body creates a stunning effect in a large school against a dark background. Small groups look insignificant.
• Blackwater tank specialists. Green neons look their absolute best in tannin-stained water with dark substrate and subdued lighting. Under standard bright aquarium LEDs on white gravel, they lose most of their visual impact.

Habitat

Native to the upper Rio Negro and upper Orinoco basins in Brazil, Venezuela, and Colombia. Found in extremely soft, acidic blackwater (pH 3.5-6.0, GH below 2) stained dark brown by dissolved tannins. These are among the most mineral-poor waterways in the world. The species (Paracheirodon simulans) is closely related to the neon tetra (P. innesi) and the cardinal tetra (P. axelrodi) but is the least known of the three. The body has a bright blue-green iridescent stripe running from the head to the caudal peduncle, similar to a neon tetra but with more green than blue and less red below. The overall appearance is more subdued than a cardinal tetra but in a proper blackwater setup with a large school, the effect is arguably more natural and atmospheric. Males are slimmer; females are slightly rounder. Adult size is about 2–2.5 cm, smaller than the other two Paracheirodon species. All green neons in the trade are wild-caught from the Rio Negro and Orinoco; the species is not commercially bred. This means supply fluctuates with seasonal collection schedules and they're more expensive than farm-bred neons or cardinals.

Breeding

Not bred commercially or by most hobbyists. The species requires extremely soft, acidic water (pH below 5.5, GH effectively zero, conductivity below 30 microsiemens) that is difficult to achieve and maintain in a home setup. Wild breeding occurs during seasonal flooding when water parameters reach these extremes. Eggs are light-sensitive and fungus quickly in anything other than near-sterile, extremely soft water. A few dedicated hobbyists have reported spawning by conditioning groups in RO water acidified with peat extract, but consistent, repeatable breeding is not established. The difficulty matches or exceeds that of cardinal tetras. For the foreseeable future, all green neons will continue to be wild-caught.

Common problems

Acclimation shock is the biggest killer. Wild-caught fish coming from pH 4 water into a dealer's tank at pH 7 and then into a keeper's tank at pH 6.5 experience cumulative osmotic stress. Slow drip acclimation over 2+ hours is essential. In soft acidic water, they're surprisingly hardy once established. In hard alkaline water, they survive but show washed-out color and shortened lifespan. The species is essentially useless as a display fish outside of soft-water setups; the green-blue stripe that makes them spectacular in blackwater conditions becomes a faint silver line under standard conditions. Ich is a risk during acclimation; treat with temperature elevation rather than chemicals. Internal parasites from wild-caught specimens cause wasting; treat with praziquantel. Neon tetra disease (Pleistophora) can affect this species as well.

Bioload

Bioload coefficient: 0.8 (tiny fish; negligible individual waste).

Bioload coefficients are calibrated against the neon tetra as the anchor (1.0). See the methodology page for the formula and how each value was derived.

Further reading

• How to cycle a fish tank
• Stocking ideas by tank size