Holger Krisp · CC BY 3.0 · Wikimedia Commons (cropped)

Freshwater Fish · Tetras

Neon Tetra

Paracheirodon innesi

Schooling characin for mature, planted tanksIntermediate

Lifespan: 5-8 years
Size: 1.2-1.5 in
Social needs: Schooling; keep 10+ together
Time: 10-15 min daily; weekly water change
Cost: Low
Diet: Omnivore (micro-flake, small pellet, live foods)

Overview

What is this animal?

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.

Temperament

Neons are peaceful, timid schooling fish that should be kept in groups of ten or more.
In a study of group size in common aquarium fish, neons kept in groups of ten shoaled most and darted least.

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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

Enclosure

Minimum 15 gallons, for a group of 10

Cannot be kept alone. The minimum is 10, and the space above is for that group.

Keep a school of ten or more in a cycled, planted tank of at least 15 US gallons and 24 in long, held at 70-79°F 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.

Check your enclosure

Supplies

Setup

Tank and stand
Filter
Heater and thermometer
Substrate, plants and decor
Liquid test kit
Dechlorinator and starter supplies

Ongoing

Micro-pellet or finely crushed tropical flake
Frozen daphnia and cyclops
Frozen or live baby brine shrimp
Microworm culture (optional, for fry and conditioning)
Spirulina-based flake

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Fine net for removing leftovers
Small feeding spoon for accurate pinches

Safe substrate: Fine, smooth sand · Smooth, rounded fine gravel (not for loaches or sand-sifting cichlids; sand is better for corydoras) · Bare bottom (quarantine and grow-out only)

Work out the cost

Care routine

Daily

Check temperature and equipment
Feed
Head-count and look everyone over

Every few days

Top up evaporationevery 3 days

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Weekly

Count the school
Test the water
Water change and gravel vacuum
Wipe the front glass only

Every few weeks

Trim and thin the plantsevery 2 weeks

Monthly

Check supplies and reagent dates
Replace or recharge chemical media, if you use any (skip it in a blackwater tank)
Rinse the filter media

Health review: Quarterly school and stability review, every 3 months

Tools

Is your enclosure big enough?Check your measurements against the recommended size What will it cost?Setup, monthly and over its whole life, itemised Is this ammonia reading dangerous?Works out the toxic part from your pH and temperature

Care in depth

Diet

Omnivore (micro-flake, small pellet, live foods)

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

Signs of good health, and the common problems

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.

Is this urgent?

6 warning signs and how fast to act, 3 of them right away

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 with fast gill movement, or crowding the filter outflowIncrease surface movement now (gently in a betta or gourami tank, without creating a strong current), then test the water. Either the oxygen has crashed or the gills are being chemically burned. Both are hours-scale problems. Bettas, gouramis and corydoras rise to gulp air as part of normal breathing; the warning is constant gulping, fast gill movement, or the whole group hanging at the top.

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 usually point at the water or the equipment rather than a pathogen, so rule those out first.

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.

Bedding and substrate

3 safe, 4 with a caveat, 2 to avoid

Substrate in an aquarium is a filter as much as a floor. Most of the biology lives in and on it.

Safe

Fine, smooth sandCorrect for corydoras, kuhli loaches, eartheaters such as rams and acaras, and anything else that sifts or burrows. Barbels wear away on sharp gravel.

safe

Smooth, rounded fine gravel (not for loaches or sand-sifting cichlids; sand is better for corydoras)Rinse thoroughly before use. Grain size should be too large to swallow and too small to trap food. Kuhli loaches need sand to burrow into and rams and acaras sift mouthfuls of it; bronze and panda corydoras manage on smooth fine gravel, but sterbai corydoras need sand.

safe

Bare bottom (quarantine and grow-out only)Legitimate for quarantine and grow-out tanks. Easy to clean, but it holds far less biological filtration, and it is no long-term home for burrowing loaches or sand-sifters.

safe

With a caveat

Crushed coral or aragoniteDeliberately raises hardness and pH. Correct for rift-lake cichlids, wrong for soft-water species.

with a caveat

Aquasoil for planted tanksExcellent for plants, but most active soils soften the water and pull pH and KH down for months, and many leach ammonia for the first weeks. Right for soft-water species; wrong for hard-water animals (livebearers, rainbowfish, goldfish, and snails, whose shells erode in soft, acidic water) unless you test GH and KH and remineralise. Cycle around it; do not stock into it.

with a caveat

Very deep sand bedsAnaerobic pockets form below about 2 inches in still sand. Either keep it shallow or keep it stirred.

with a caveat

Painted or coated gravelUsually fine, but coatings chip. Test a handful in a jar for a week first.

with a caveat

Never

Sharp or angular gravel with bottom-dwellersWears down barbels and leads to infection in corydoras and loaches.

never

Anything containing metal, limestone of unknown origin, or shells in a soft-water tankSlowly alters chemistry in ways that are hard to diagnose later.

never

This is our general list for freshwater fish. We have not built one specific to Tetras yet.

Top resources for more info

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