Zebra danio
Also known as Zebrafish, Zebra fish, Danio rerio
- Adult size
- About 4–5 cm
- Lifespan
- 3–5 years
- Origin
- Rivers, streams and rice paddies of South Asia, including India, Bangladesh and Nepal
- Company
- Keep in a shoal of at least 6
- Energetic
- Hardy
- Playful
- Fast
About the Zebra danio
The zebra danio is a small, striped fish known for its boundless energy. It is also one of the most important animals in scientific research, where it is studied for genetics and development.
Zebra danios are hardy and tolerate a fairly wide range of temperatures, which once made them a common choice for cycling new tanks. Today, fishless cycling is recommended instead, as putting fish into an uncycled tank exposes them to harmful ammonia and nitrite.
Long-finned and leopard-spotted varieties are widely available. Genetically modified fluorescent versions also exist, but their sale is restricted or banned in some countries.
Temperament
Zebra danios are peaceful but very lively, constantly chasing one another in fast bursts. Kept in small numbers they can become nippy towards other fish, so a proper shoal helps keep their energy directed at each other. They suit tanks with other active fish and may stress slow, long-finned species.
Tank & water
A shoal of zebra danios needs a tank of at least around 60 litres, preferably long rather than tall, to give swimming room. They are comfortable at roughly 18–25°C, so a heater is often useful but they do not need very warm water. Moderate water flow and good oxygenation suit them, and a lid is essential as they jump. Leave plenty of open space with plants around the edges.
Diet
Zebra danios eat almost anything, readily taking flake, small pellets and frozen or live foods. They feed mostly near the surface and in mid-water. Offer small portions once or twice daily, varying the diet with foods such as daphnia and brine shrimp.
Behaviour & tank mates
Their main need is space to race around, ideally with a gentle current to swim against. A large shoal shows constant social interactions and chasing that is fascinating to watch. Plants provide occasional cover and resting places.
Tank maintenance
Change about a quarter of the water weekly and vacuum the substrate. Keep the lid in place during maintenance as much as possible to reduce jumping.
Health
Zebra danios are among the hardiest aquarium fish but can still develop white spot, fin rot and bacterial infections. Spinal curvature is occasionally seen, sometimes linked to genetics, age or infection. As always, test the water first and speak to an aquatic vet or specialist if illness spreads.
Prone to
- White spot (ich)
- Fin rot
- Bacterial infections
- Spinal curvature
Call a vet if you notice
- Gasping at the surface — test the waterEmergency
- Fish found outside the tank or with jump injuries
- A suddenly bent spine
- White spots or cottony growths
- A normally active fish hanging motionless
An aquatic vet or experienced aquatic specialist is best placed to help. Find one before you need them.
Common questions
Are zebra danios fin-nippers?
They can nip when kept in small groups or with slow, long-finned fish. In a proper shoal with active tank mates, this is much less likely.
Do zebra danios need a heater?
They tolerate cooler water than most tropical fish, so in a warm room a heater may not be essential. A heater does help keep temperature stable, which is good for any fish.
Should I use zebra danios to cycle a tank?
No. Adding fish to an uncycled tank exposes them to ammonia and nitrite, which cause suffering. A fishless cycle is the kinder method.
Written by the Petopedia editorial team to our editorial standards. General guidance, not veterinary advice.