Zebra Danio (Danio rerio)

Choose the classic striped zebra danio

The zebra danio, Danio rerio, is the original blue-and-gold striped danio: five even, dark blue stripes run from behind the gill cover to the end of the tail, separated by pale gold bands. Hamilton described it in 1822 from the Kosi River, a tributary of the Ganges, and older books call it Brachydanio rerio. It is also sold as the zebrafish, striped danio or simply zebra. Few aquarium fish are better known: Practical Fishkeeping counts more than 5,000 scientists in over 450 laboratories who work with the species.

FishBase places Danio in the family Danionidae, while Seriously Fish and OATA still list it under Cyprinidae, the older and wider carp family. Wild zebra danios come from South Asia. Seriously Fish says current knowledge points to India, Bangladesh and possibly Bhutan, and that older records from Pakistan, Nepal and Myanmar may be misidentified similar species; FishBase still lists those countries. The IUCN assesses the species as Least Concern.

Decide from the complete care picture

This listing is the classic striped form. The leopard, long-finned and golden zebra danios are the same species with the same care. Compare it with the rest of our rasboras and danios, or browse every Danio species we stock. Some gallery images are representative and none shows the exact fish supplied.

Select the quantity for a full shoal

One purchase quantity supplies one live zebra danio in our single standard size. Sex is not specified. Zebra danios are shoaling fish, so choose the quantity for the whole group you plan to keep, not for one fish.

Work from the shoal you intend to keep

• One unit: one zebra danio. Not a group on its own.
• Five units: the minimum group in OATA’s danio care sheet.
• Eight to ten units: the group size Seriously Fish recommends; larger groups are calmer and show better colour.
• More than ten: a fine display, provided the aquarium length and filtration allow for every adult.

Seriously Fish notes that mature females are usually rounder-bellied, a little larger and slightly less colourful than males, and that the differences are clearest at spawning time. Plan the shoal without relying on a particular mix of males and females.

Prepare the aquarium for the whole group before you order, and check our delivery and Live Arrival Guarantee terms for dispatch days.

Plan the aquarium around an active adult

Seriously Fish gives a maximum of 5 cm standard length (measured without the tail), OATA says most danios reach about 5 cm, and FishBase records 3.8 cm standard length. Plan for fish of about 5 cm.

The sources also differ on tank size. Seriously Fish recommends a base of at least 90 × 30 cm, about 81 litres, because the species is so active; OATA suggests at least 45 litres for a small shoal of the smaller danios and at least 120 litres for danios of 5 cm and over; FishBase gives a minimum tank length of 60 cm. We follow Seriously Fish’s 90 × 30 cm base as the practical minimum for a group of eight to ten, and go larger when other fish share the tank.

Use a three-step space check

1. Measure the length: zebra danios swim end to end all day, so a long tank matters more than a tall one.
2. Count the full shoal: add every other fish in the aquarium at adult size, not the size it arrives at.
3. Check the filter capacity: a shoal of ten adds steady waste; the filter must cope with the final stock, not the first week’s.

Our stocking calculator checks a planned community against your tank size before you buy. Fit a cover as well, because startled danios can jump, and leave the tank lights on a regular day-and-night timer.

Arrange plants around open swimming water

Seriously Fish describes the décor as “not especially critical”, but notes that colour shows best in a heavily planted tank with a dark substrate, and suggests floating plants and driftwood roots or branches to diffuse the light. Practical Fishkeeping adds that wild zebra danios favour turbid water with limited visibility, and that laboratory fish prefer darker areas.

Divide the footprint by function

Gentle to moderate water movement is enough. Practical Fishkeeping points out that the zebra danio’s restlessness is often misread as a need for fast water, whereas wild fish live mostly in slow or still water; OATA recommends a moderate current for oxygen. If you are new to live plants, our easy live plants guide lists hardy choices that suit a danio tank.

Set zebra danio water values inside the species range

The zebra danio is famously adaptable. Seriously Fish reports native water reaching 24.6–38.6°C in July, and Practical Fishkeeping describes wild fish found from 6°C to 39°C and in water from pH 5.1 to 8.2. Those extremes show what the species survives in the wild; they are not targets for an aquarium. Keep it stable inside the ranges below.

Separate habitat values from waste readings

Seriously Fish and OATA both say a heater is not always needed. If your room falls below 18°C at night or in winter, fit a thermostatic heater and set it within the range, checking with a separate thermometer. Compare your tap water with these values in our water matcher rather than adjusting chemistry blindly: stability matters more than hitting one exact number.

Build filtration for the whole shoal

Seriously Fish suggests a filter rated at four to five turnovers an hour, which for an 81-litre aquarium is about 325–405 litres per hour, and a heater of about 50 W where the room sits around 20°C. The filter’s real job is biological: its bacteria convert toxic ammonia into nitrite and then into the less harmful nitrate, so it must run all the time.

Follow a weekly maintenance sequence

1. Test ammonia, nitrite, nitrate, pH and hardness, as OATA recommends, before any maintenance.
2. Change 25% of the water at least once a week.
3. Treat the replacement water with tap-water conditioner before it goes in.
4. Siphon debris from the open areas of the substrate.
5. Check the filter flow and clear blocked intakes.
6. Rinse filter media in removed tank water, never under the tap.

A new aquarium must be cycled before the shoal arrives. OATA warns that adding too many fish too quickly causes ammonia and nitrite spikes, sometimes called new tank syndrome; our guide to the fish tank nitrogen cycle explains how to mature a filter. Clear water is not proof of safe water, so keep testing.

Feed small varied meals once a day

In the wild, zebra danios are micropredators. Seriously Fish lists small aquatic crustaceans, other invertebrates and mosquito larvae, and FishBase adds worms and insect larvae. In the aquarium they are unfussy and take a good dried food readily; OATA describes danios as omnivorous.

Build one measured meal

• Staple: a good-quality flake or small granule every day.
• Variety: small live or frozen foods such as daphnia, brine shrimp or bloodworm a few times a week.
• Amount: only what the shoal eats within a few minutes, once a day, as OATA advises.
• Spread: scatter food across the surface so every fish gets a share, not just the quickest.

Zebra danios feed fast at the surface and in midwater. If you keep slow bottom-dwelling fish with them, give those fish their own sinking food so the danios do not take it all. A sudden loss of appetite in the shoal is a warning sign: test the water before changing the food.

Introduce the shoal and watch the first week

Introduce the fish only to a mature, cycled aquarium with ammonia and nitrite at zero. OATA recommends the floating-bag method of acclimatisation and warns against leaving fish in the transport bag for long; our guide to acclimatising new fish walks through it.

Use a first-week checkpoint plan

OATA describes healthy danios as having clear, bright eyes, undamaged fins, intact scales, normal swimming and steady breathing. Watch for hanging at the surface, sitting on the bottom, erratic swimming, colour change, white spots or fluffy growths, and loss of appetite.

Seriously Fish warns about three problems seen in mass-bred zebra danios: neon tetra disease, a microsporidian infection that is essentially untreatable once advanced; “skinny disease” caused by Pseudoloma neurofilia; and Flavobacterium columnare infections, which can look similar. A fish that keeps losing weight despite eating, or develops pale patches, should be separated and assessed, and the rest of the shoal watched closely.

Keep a complete, confident zebra danio shoal

Seriously Fish describes the zebra danio as a schooling species to be kept in groups of at least eight to ten. In larger groups the fish are less nervous and more colourful, as males compete for the attention of females. OATA puts its minimum at five and warns that danios kept singly or in small groups often become stressed. Browse other schooling fish if you plan a tank built around shoals.

Balance three connected limits

• Social limit: at least eight, and ideally ten or more.
• Space limit: a base of at least 90 × 30 cm, larger when other shoals share the tank.
• Biological limit: ammonia and nitrite at zero as the filter catches up with every addition.

Chasing within the shoal is normal display behaviour, especially between males. Act if one fish is persistently singled out and cannot feed or rest; more cover and a larger group usually spread the attention.

Screen every tank mate before mixing

Seriously Fish calls the zebra danio very peaceful and compatible with other small cyprinids, tetras, livebearers, rainbowfish, anabantoids (gouramis and their relatives), catfish and loaches, provided adult sizes and water needs match. OATA adds that the danios’ constant activity can stress timid species, and Practical Fishkeeping notes that goldfish have eaten young danios.

Check suits and avoid before you buy

Good companions in our range include the Pearl Danio, Kerr’s Blue Danio and Rosy Danio, and, for a cooler tank, White Cloud Mountain Minnows. Our tank mates tool checks the mix for you.

Know the colour forms and the breeding basics

The leopard danio is a spotted form of the same species. Seriously Fish explains that it was once described as Brachydanio frankei but is a spontaneous mutation that also occurs in the wild. Long-finned, golden and “Russian long-fin blue” forms are bred for aquariums; the golden forms are leucistic, not albino. GloFish are transgenic zebra danios: Seriously Fish notes that they are illegal to buy, sell or keep in the European Union, and Practical Fishkeeping says genetically modified livestock may not be imported into the UK. We do not sell them.

Breed them in a separate spawning tank

Zebra danios scatter their eggs and give no parental care, and the adults eat any eggs they find. Seriously Fish suggests a small, dimly lit spawning tank with mesh, plastic grass matting or Java moss on the base so the eggs fall out of reach, slightly acidic to neutral water at the warm end of the range, and a well-conditioned pair, which usually spawn the following morning. Remove the adults afterwards.

Seriously Fish gives an incubation time of 24–36 hours, while the standard laboratory staging work by Kimmel and colleagues (1995) places hatching between 48 and 72 hours after fertilisation, and OATA simply says the eggs hatch in a couple of days. Either way, Seriously Fish notes that the fry become free-swimming a few days after hatching. Feed the fry infusoria-grade food first, then brine shrimp nauplii or microworm. FishBase reports that domesticated zebra danios live 3.5 years on average, and the oldest recorded reached 5.5 years.

Answer zebra danio buying questions

How many zebra danios should I keep?

At least eight to ten, as Seriously Fish recommends; OATA’s minimum for danios is five. Larger groups are calmer and show better colour.

Do zebra danios need a heater?

Not always. Seriously Fish gives 18–25°C and OATA 17–27°C for danios, so a warm room may be enough. Fit a thermostatic heater if your room falls below 18°C.

What size tank do zebra danios need?

We recommend a base of at least 90 × 30 cm, about 81 litres, for a shoal, following Seriously Fish. OATA suggests at least 120 litres for danios of 5 cm or more, and FishBase gives a 60 cm minimum length.

How big do zebra danios get?

About 5 cm standard length, according to Seriously Fish and OATA. FishBase records a maximum of 3.8 cm standard length.

Is the leopard danio the same species?

Yes. The leopard danio is a spotted form of Danio rerio that also occurs in the wild. It was once described separately as Brachydanio frankei.

What do zebra danios eat?

A good-quality flake or small granule every day, with small live or frozen foods such as daphnia, brine shrimp and bloodworm. Feed once a day, only what they finish in a few minutes.

Which fish can live with zebra danios?

Peaceful community fish that share 18–25°C: other danios, small barbs and rasboras, tetras, livebearers, rainbowfish, gouramis, catfish and loaches. Avoid goldfish and any fish large enough to eat them.

How long do zebra danios live?

FishBase reports an average of 3.5 years for domesticated zebra danios, with the oldest recorded at 5.5 years.

Do you sell GloFish?

No. GloFish are transgenic zebra danios. Seriously Fish notes they are illegal to buy, sell or keep in the European Union, and Practical Fishkeeping says genetically modified livestock may not be imported into the UK.

Consult the care references

• Seriously Fish: Danio rerio — names, distribution, habitat, adult size, aquarium base, water values, diet, group size, compatibility, sex differences, breeding, colour forms and health warnings.
• FishBase: Danio rerio — family, distribution, environment values, maximum length, diet, breeding cues, lifespan and IUCN status.
• OATA: How to look after danios and white cloud mountain minnows — UK care-sheet tank size, group size, water-quality limits, feeding, maintenance and health signs.
• Practical Fishkeeping: Zebra danios, used, abused, unique — wild habitat, temperature and pH extremes, behaviour, research use and the UK position on GM fish.
• Kimmel et al. (1995): Stages of embryonic development of the zebrafish — laboratory hatching period of 48–72 hours.