Neon Fish (Neon Tetra): Care, Tank Mates and Why It Glows

When people search for a neon fish they almost always mean the neon tetra, Paracheirodon innesi, a small schooling fish from the western and northern Amazon basin in Colombia, Peru and Brazil (Wikipedia). It grows to about 4 cm (1.6 in) and has a light-blue back, a silver-white belly, an iridescent blue stripe from the nose to the adipose fin, and a red stripe from mid-body to the base of the tail.

It is one of the most traded aquarium fish. Wikipedia reports about 2 million sold in the US each month, and says fewer than 5% of those sold in America are wild-caught: more than 1.5 million a month are imported from fish farms, mostly in Southeast Asia. The species was described in 1936 by George S. Myers and named after the aquarium writer William T. Innes (Wikipedia).

For care that applies to all tetras, such as how many to keep and tank size, see our tetra fish page. This page covers what is specific to the neon.

A neon tetra does not make its own light. Its stripes shine because cells in the skin contain guanine crystals that reflect light (Wikipedia). That is why the colour depends on the lighting: Wikipedia describes a light-adapted state that looks blue-green and a dark-adapted state that looks indigo, and at night the blue and red stripes turn grey or black while the fish rests.

So a neon that looks dull first thing in the morning is not necessarily ill. A neon that stays pale all day is a different matter; loss of colour is one of the listed signs of neon tetra disease (see below).

They are sold as beginner fish, but they are less forgiving than that label suggests. PetSmart rates the neon tetra as a beginner fish and calls it hardy. Wikipedia gives the details that decide whether they thrive:

• Water: 22 to 24 C (72 to 76 F), pH 6.0 to 7.0, general hardness below 10 dGH, carbonate hardness 1 to 2 dKH, nitrate under 20 ppm
• Tank: at least 10 US gallons (38 L)
• Lifespan: usually only two to three years in an aquarium, although up to ten is possible in ideal conditions
• Disease: neon tetra disease, caused by the microsporidian parasite Pleistophora hyphessobryconis, is generally incurable and often fatal, but generally preventable. Signs include restlessness, loss of colour, cysts, trouble swimming and a curved spine.

The practical advice follows from that: buy from a shop whose neons are active and fully coloured, and quarantine new fish before adding them to an established group.

Breeding them at home is hard. Wikipedia lists dim light, very soft water below 1 dH, pH around 5.5 and 24 C (75 F) as breeding conditions.

Choose small, peaceful fish. PetSmart lists community danios, rasboras, catfish and the less aggressive barbs and gouramis as good company, and suggests adding top and bottom swimmers because neons occupy the middle of the tank.

The firm rule is size. A neon is about 4 cm long (Wikipedia), so any tank mate large enough to swallow it is a risk however calm it seems. Keep the neons themselves as a proper group: at least six, and eight to 12 or more is better (Wikipedia). Our zebra danio page covers one of the most common companions.

Four similar fish are sold side by side, and they are separate species (Wikipedia):

• Neon tetra, Paracheirodon innesi: the red stripe runs only from mid-body to the tail
• Cardinal tetra, Paracheirodon axelrodi: the red extends much further, along nearly the whole lower body
• Green neon tetra, Paracheirodon simulans: a distinct species, not a colour variety of the neon
• Black neon tetra, Hyphessobrycon herbertaxelrodi: a different genus altogether

The difference matters for care. On LiveAquaria's tetra page (checked 25 September 2026) the cardinal tetra is marked Expert Only.

GloFish are genetically modified, and some governments do not allow genetically modified fish to be sold. Wikipedia explains that the colour comes from a gene for green fluorescent protein, originally from a jellyfish, inserted into zebrafish embryos, with other colours using genes from sea coral.

• European Union: import, sale and possession are not permitted. Wikipedia records that in November 2006 Dutch authorities found 1,400 illegal fluorescent fish in aquarium shops.
• California: sales were prohibited from 2003 under rules on genetically modified fish, and the rules were lifted in 2015 (Wikipedia).

The neon tetra is not one of them. Its shine is natural reflection. Wikipedia lists the GloFish species as the zebrafish, black tetra, tiger barb, rainbow shark, Siamese fighting fish, X-ray tetra, bronze corydoras and freshwater angelfish. Laws differ by country and state, so check your local rules before buying.

Prices seen at two US retailers on one day. Check how many fish each listing includes before comparing:

• PetSmart: neon tetra $2.99
• LiveAquaria: neon tetra from $24.99, cardinal tetra from $29.99, black neon tetra from $21.99 on sale (regular $49.99). These listings have quantity options, so the starting price may cover more than one fish.

Research and drafting for this page were assisted by AI and checked line by line against the sources listed below. Every number names the organisation it comes from, and where sources disagree we say so instead of picking one silently. Prices are given with the date we checked them (25 September 2026); they change, so confirm before you rely on them. If you find an error, tell us and we will correct it.