Neon tetras are small characins from the soft, shaded blackwater streams of the upper Amazon, known for the blue and red stripe along their flanks.
In a tight school under good conditions they show their colour best.
Though cheap and widely available, they are more demanding than their price suggests.
They need a mature, stable aquarium and the security of a large group, and they are often lost early in newly set-up or under-stocked tanks.
Housing
Keep a school in a cycled, planted tank of at least 57 litres (15 gallons), held at 21-26C (70-79F) in soft, slightly acidic water.
Neons colour up and feel safe in dim, well-planted surroundings with darker substrate and gentle filtration.
Stability is essential; they do poorly in newly cycled tanks or fluctuating parameters.
Add them only to a mature aquarium, keep nitrate low with weekly water changes, and avoid bright, bare setups that leave these shy fish stressed and washed-out.
Diet
Neons are micro-predators and omnivores with small mouths.
Feed a finely crushed flake or micro-pellet staple and supplement frequently with small frozen or live foods such as daphnia, cyclops, microworm, and baby brine shrimp to maintain colour and condition.
Offer tiny pinches once or twice daily, only what is eaten quickly.
Their small size makes overfeeding easy and quickly fouls the soft, lightly buffered water they prefer, so feed sparingly and remove any uneaten food.
Health
Neon tetra disease, an incurable parasitic wasting illness causing fading colour, curved spine, and lumps, is the species' notorious affliction.
There is no cure, so prevention through quarantine, low stress, and removing affected fish is essential to protect the school.
Mass production has weakened many farmed lines, so neons are best added to mature tanks and acclimatised slowly.
Common stress-related issues include ich and fin rot; stable, soft water and an established aquarium give the best resistance.
Temperament
Neons are peaceful, timid schooling fish that should be kept in groups of at least eight to ten, ideally more.
In small numbers they become stressed, pale, and reclusive, while a large school is more confident and coordinated.
They suit calm community tanks with other small, gentle species and should never be mixed with large or aggressive fish that may eat them.
Their nervous nature means sudden movements and bright bare tanks leave them hiding rather than displaying.
A good fit for
Established, mature planted aquariums
Peaceful community tanks of small species
Keepers wanting a schooling display
Soft, slightly acidic water setups
Common mistakes to avoid
Adding to brand-new, uncycled tanks
Keeping too few and stressing the school
Neon tetra disease spreading without quarantine
Housing with large or aggressive tankmates
Is your enclosure big enough?
Minimum volume57 litres (15 US gallons)
CompanyCannot be kept alone. The minimum is 8, and the space above is for that group.
In a fish tank the patient is usually the water. Test before you treat — dosing a healthy tank for a disease it does not have makes things worse.
Go now
Any detectable ammonia or nitrite in a stocked tankLarge water change now with dechlorinated, temperature-matched water. Stop feeding. Test again in 12 hours. Both are directly toxic. How toxic the ammonia reading is depends on pH and temperature, so the same number can be harmless or lethal.
Now
Fish gasping at the surface, or crowding the filter outflowIncrease surface agitation immediately, then test the water. Either the oxygen has crashed or the gills are being chemically burned. Both are hours-scale problems.
Now
Sudden deaths, more than one fish in a dayTest ammonia, nitrite, nitrate and temperature before doing anything else. Do not add medication yet. Multiple simultaneous deaths point at the water or the equipment, not at a pathogen.
Now
Today
Flashing — repeatedly scraping against decor or substrateTest the water, then look closely for parasites. Irritation is either chemical or parasitic; the test tells you which before you medicate.
Today
White salt-grain spots over the body and finsBegin the appropriate treatment today and check the temperature. The parasite's life cycle is temperature-driven, and it multiplies with every cycle you wait.
Today
Soon
Clamped fins, hiding, or refusing food for more than two daysTest the water and review recent changes. Usually the earliest visible sign of a parameter drifting.
A few days
Never add a new fish to a tank that is not fully cycled, and never treat blind. A test kit is cheaper than the fish.
This is general guidance for a healthy adult, not a diagnosis. An exotics vet who knows your animal always overrides it — and the time to find one is before you need one.
What it really costs
Setup, monthly, first year and across a whole life, itemised and with the electricity worked out from the actual wattage. Published figures for the same animal disagree by a factor of four, so the calculator shows ranges rather than picking one.
Intermediate
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Beginner
Intermediate
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Intermediate