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.

Feeding

Small mouths limit food size. Micro pellets, crushed flake, and frozen daphnia or baby brine shrimp are staples. Frozen bloodworm is accepted but chop it first; whole bloodworms are too large for most neons to swallow. Feed small amounts twice daily rather than one large feeding. Neons are midwater feeders and generally ignore food that sinks to the bottom, so pair them with bottom feeders like corys to clean up leftovers.

Compatibility

• Stressed by aggressive or boisterous tankmates, even non-predatory species. Tiger barbs and serpae tetras cause constant fin damage.
• Classic community fish with corydoras, small rasboras, honey gouramis, and other calm species. Avoid anything large enough to eat them (angelfish will, despite being sold alongside neons in stores).
• Adult neons may pick at very small shrimp fry but ignore adult cherry shrimp and amano shrimp.
• Susceptible to neon tetra disease (Pleistophora hyphessobryconis), which is incurable and contagious. Quarantine all new neons for 2-3 weeks before adding to an established group.

Origin and habitat

Paracheirodon innesi, the neon tetra, is a tiny, brilliantly coloured characin from the western Amazon, recorded around Leticia in Colombia and Tabatinga in Brazil, the lower Rio Putumayo, and small streams feeding the Solimoes. Its exact range is still poorly mapped, partly because the type specimens came from an aquarium shipment labelled only as near Iquitos. George Myers described it in 1936 and named it for the American aquarist and publisher William T. Innes. It lives in soft, acidic black and clear waters, where the glowing blue lateral stripe helps the fish stay together in dim, tannin-stained streams. After decades in the family Characidae it was placed, in a 2024 revision of the American characins, in the family Acestrorhamphidae. It is one of the most heavily traded aquarium fish in the world, with well over a million imported into the United States every month, the great majority farmed in Southeast Asia, and farmed stock copes with a wider range of water than wild fish. Adults reach about 4 cm.

Breeding

Breeding is possible but fiddly. Neons need very soft, acidic water, near pH 5.5 with almost no hardness, dim light, and a separate tank with fine-leaved plants or a spawning mop, and a conditioned pair usually spawns at first light. The eggs are sensitive to light and the parents eat them, so the adults come out straight after spawning. Eggs hatch in about a day, and the fry need infusoria-grade food for the first week before moving to baby brine shrimp. Most keepers never bother, since the water chemistry is demanding and farmed neons cost next to nothing.

Common problems

Neon tetra disease is the one most associated with the fish: a microsporidian parasite, Pleistophora hyphessobryconis, that the fish takes in by mouth and that settles in the muscle, causing fading colour, lumpy bodies, erratic swimming, and death. It has no cure and spreads to other neons, so affected fish should be pulled out at once; a bacterial look-alike sometimes called false neon tetra disease does respond to antibiotics. New fish often arrive with ich after transport, treatable with heat or medication. The most common complaint, though, is simpler: neons are sensitive to ammonia and nitrite and are usually the first to die in a tank that is not properly cycled, which is why beginner reports of neons dying off almost always trace back to water quality.

Bioload

Further reading

• Why your angelfish ate your neons
• Blackwater tanks: replicating acidic jungle streams
• How bioload actually works