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: 3-4cm / 1.2-1.5in
Social needs: Schooling; keep 8-10+ 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 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

Enclosure

Minimum 57 litres (15 US gallons) — for a group of 8

Cannot be kept alone. The minimum is 8, and the space above is for that group.

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.

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
Fine net for removing leftovers
Small feeding spoon for accurate pinches

Safe substrate: Inert aquarium gravel · Fine, smooth sand · Aquasoil for planted tanks

Work out the cost

Care routine

Daily

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

Weekly

Top up evaporationevery 3 days
Clean glass and clear algae
Count the school
Test the water
Water change and gravel vacuum

Monthly

Trim and thin the plantsevery 2 weeks
Check supplies and reagent dates
Rinse the filter media

Less often

Replace chemical filter media (Carbon/Purigen)every 2 months

Vet: Quarterly school and stability review — every 3 months

Top resources for more info

Independent creators and organisations we would send a friend to. We have no affiliation with any of them, and nothing here is sponsored. Links checked 2026-09-19.

YouTubers

Girl Talks FishCare how-tos by fish type, tank setup and beginner mistakes Aquarium Co-OpSpecies care guides, filtration and fish health (run by a retailer)Prime Time AquaticsSpecies profiles, stocking and water chemistry explained plainly

Sites

Seriously FishSpecies profiles with tank size, water parameters and diet for 1,800+ fish Practical FishkeepingLong-running UK fishkeeping magazine with care and species articles FishLoreCare profiles and a large keeper forum for freshwater and saltwater fish

Go deeper

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.

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.

Length

Width

Height

Units

Or tank volume

Units

Is this urgent?

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.

Region

How many animals

Your electricity price, per kWh

Buying the setup

Bedding and substrate

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

Safe

Inert aquarium gravelRinse thoroughly before use. Grain size should be too large to swallow and too small to trap food.

safe

Fine, smooth sandCorrect for corydoras, kuhli loaches and anything that sifts. Their barbels wear away on sharp gravel.

safe

Aquasoil for planted tanksExcellent for plants, but it leaches ammonia for the first weeks. Cycle around it; do not stock into it.

safe

Bare bottomLegitimate for quarantine and grow-out tanks. Easy to clean, but it holds far less biological filtration.

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

Very deep sand bedsAnaerobic pockets form below about 5 cm 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.

My kit says 0.25 ppm. Is that dangerous?

A liquid kit measures total ammonia, but only the un-ionised fraction is really toxic, and that fraction is governed by pH and temperature — each whole pH unit multiplies it roughly tenfold. So the same reading can be nearly harmless in one tank and lethal in another; this works out which one you are in.

Total ammonia, ppm

Temperature, C