Green neon tetra

Water parameters

Tolerated range for this species. Aim for the middle of each band rather than the extremes.

Tank and habitat

Substrate: any.

Behavior

Plant interaction: plant safe.

Typically wild-caught; acclimate slowly.

Feeding

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.

Origin and habitat

Paracheirodon simulans is the smallest of the three common Paracheirodon tetras, a blackwater specialist from northern South America. It turned up by accident at the end of 1962 in a shipment of cardinal tetras sent from Manaus to Zurich, and Jacques Gery described it the following year as Hyphessobrycon simulans; Weitzman and Fink moved it into Paracheirodon in 1983 on the basis of dental and fin-ray characters, a placement later backed by genetic work. Its range covers the middle and upper Rio Negro, upstream of the mouth of the Rio Branco, and a stretch of the Orinoco system along the Venezuela-Colombia border between San Fernando de Atabapo and the mouth of the Rio Meta. Unlike the neon and cardinal tetras, it lives only in blackwater, in the soft, acidic, tannin-stained upper tributaries. Records give a maximum of about 2 cm standard length, with other sources putting total length nearer 2.5 to 3.5 cm. The fish is marked by a blue-green stripe that runs to the tail base, with only a little red near the tail, and its colour shifts with conditions, paling in bright light and dulling toward violet at night. Its range overlaps the cardinal tetra's, but the two are not usually found in the same water.

Breeding

Breeding is difficult and rarely done. The species needs extremely soft, acidic water, near-zero hardness and very low conductivity, the kind of conditions that occur naturally during seasonal flooding and are hard to hold steady in a tank. It is an egg scatterer, and the eggs are sensitive to light and quick to fungus in anything but very soft, near-sterile water, so a separate dim spawning tank is needed. Some keepers have raised fry by conditioning groups in RO water acidified with peat, and eggs hatch in roughly a day to a day and a half, but no reliable, repeatable method has taken hold. As a result the great majority of green neons in the trade are still wild-caught.

Common problems

Acclimation is the biggest hurdle. Wild fish move from water near pH 4 through a dealer's tank and into a keeper's tank, and the cumulative osmotic shock kills many, so slow drip acclimation over a couple of hours matters. Once settled in soft, acidic water they are surprisingly tough. In hard, alkaline water they hang on but look washed out and tend not to last, and the blue-green stripe that makes a big school striking in blackwater fades to a faint silver line. Ich can flare during acclimation and is best handled by raising the temperature rather than dosing a nano fish, and wild-caught stock can carry internal parasites that cause slow wasting.

Bioload

Further reading

• The schooling number matters more than you think