Zebrafish - Danio rerio

Zebrafish - Pictures by JJphoto.dk

Glowfish, genetically engineered and patented
zebrafish that glows in the dark.

Common name: Zebrafish, Zebra fish, Zebra danio
Scientific name: Danio rerio
Synonyms: Brachydanio rerio
Size: 6 cm / 2,4 inches
Temperature: 18 - 25 °C (65 - 77 °F )
Hardness: 7 - 12 dH
Lifespan: 5 years (usually only 2-4)

The zebra fish is a small and friendly fish. It is very hardy and adaptable which makes it an ideal beginner fish. The zebra fish is a very popular fish and you can find it in just about any aquarium shop around the world. They are breed in huge numbers for the aquarium market. It is likely possible to find locally breed specimens if you would prefer such specimens over imported fish.

The zebra fish has been a popular fish for a long time and became popular early due to its hardiness, cold resistance and easiness to breed.

The Zebrafish originates from eastern Asia. It can be found from the Ganges region in India and east through Pakistan, Bangladesh, Nepal and Burma (Myanmar). It is commonly found in most types of water ranging from streams to stagnant ponds and rice fields. The Zebra fish has also been accidentally introduced into a number of different waters around the world and it can today also be found in countries such as USA, Australia and Colombia.

There are a long row of different variants of this fish available in addition to the regular form. These forms include classical forms like long finned zebra fish, albino zebra fish, golden zebra fish, sandy zebrafish and leopard danios (earlier known as Danio frankeri.), but also modern genetically engineered zebra fish that glows in the dark. The glowing variant is available in red, yellow and green and is often sold under the name Glowfish (the name is a trademark for these patented fish). Glowfish was not designed for the aquarium market but is proving popular and might lead to more design species being develop for the hobby in the future.

The Zebrafish is very popular among scientist as they are a perfect model organism for vertebrates and can be used as a complement to mice and rats in research. The Zebrafish has proven very useful for research and the study of this fish has formed the basis for many new promising medical technologies.

This Zebrafish is a very curios species and they will try to nibble on your arm hair or on your hands when you clean the aquarium to see if they can find something to eat. They show the same behavior in the wild. 

Aquarium & care

The Zebra danio is an extremely flexible fish that will adapt to almost any setup. This is not surprising considering the wide variety of different biotopes they are found in the wild; environments ranging from stagnant pools and rice fields to fast moving streams. You can design your aquarium decoration in accordance with the needs of the other fish species you keep with your Zebra fish. They are suitable to be kept in community aquarium with all friendly species that are small enough not to consider the Zebra fish as food. Zebra fish prefers neutral to slightly acidic water.

The ideal aquarium for Zebra fish contains clean oxygen rich water and has a lot of open area to swim in and some areas with dense vegetation.

The Zebrafish is a shoaling fish and it should never be kept in groups of less than 6-8 fish. A larger group is preferable. If kept in smaller groups the fish will be timid and never show its true nature.

Feeding zebrafish

Zebra danios are omnivores. They are very easy to feed as they will accept almost any food of a suitable size. Zebra fish put very small demands on the fish keeper in regards to food. They thrive and breed on a diet of exclusively (high quality) flake food. You should however none the less try to give them a more varied and nutritious diet. Such a diet can be based around flake food but be supplemented with frozen and live food as well as vegetables.

Sexing zebrafish

Zebrafish are easy to sex once they have reached sexual maturity. The same signs can be used even before that, but it is harder to see the difference in younger fish. Females are larger and a lot fatter than the smaller sleeker males. It is very easy to tell an adult Zebra danio male from an adult female.

Breeding zebrafish

The Zebra fish is just like most other popular danio species very easy to spawn. They often spawn in community aquariums but it is rare for any fry to survive. The species is an egg scatterer that shown no parental concerns. They forget about the eggs as soon as they have been deposited and they will eat their own egg and fry.

The zebra fish can be bred both in groups and in pairs. Breeding them in pairs usually yields a better result as some fish in a group tends to eat the fry while others are spawning. If you want a large batch of fry you should start by separating the males and the females into different aquariums. You should then condition the fish by giving them a good and varied diet with a lot of live food for 2-3 weeks before taking the fattest female and the most vibrant male and move them to a breeding aquarium.

The bottom of the breeding aquarium should be covered by a mesh or two layers of marbles to protect the eggs from the parent’s hungry eyes. The aquarium should also contain batches of fine leafed plants. Sunlight and a reduced water temperature can help trigger spawning. The pair that has been moved to the aquarium will usually spawn within 24 hours. It can be good to move the female to the breeding tank first and leave her there fore 24 before adding the male. The parents should be removed from the aquarium once the spawning is complete to prevent them from eating the eggs.

The fry are rather small and should be feed infusorians or rotifers until they grow large enough to eat artemia nauplier.