Danio rerio – Zebra Danio
Since the discovery by Hamilton in 1822, Zebra Danio has been renamed several times. Consequently, currently there are seven recognized synonyms: Brachydanio rerio, Barilius rerio, Nuria rerio, Cyprinus rerio, Cyprinus chapalio, Perilampus Striatus and Danio lineautus. Their common name: Zebra Danio, is a reference to the stripes on their body.
Besides these synonyms, Danio frankei is also recognized as a synonym to Danio rerio. Scientists used to believe Danio frankei was a separate species. However, recent research showed that Danio frankei is a naturally occurring mutation of Danio rerio.
Zebra Danio has a silver coloration with blue stripes. These stripes start right after operculum and can be seen over the entire body including the caudal fin. Besides the caudal fin can this pattern be found on all the other fins as well.
The differences between the sexes can be seen on basis of the size and colors of the fish. Males tend to be smaller and slimmer. Additionally, their coloration is better looking than those of the females. This difference becomes clearer when the fish get ready for mating. At that moment the males will show even more color in order to impress the females.
On average Danio rerio can reach an age of 3.5 years in the aquarium. However, there are individuals that lived for more than 5 years.
Distribution and Habitat
Danio rerio can be found in Pakistan, Myanmar, India, Bangladesh and Nepal. They mainly inhabit rivers with little to no current. In those cases where they were found in fast flowing waters, they swam in the areas where the current was minimal.
Scientist belief that Zebra Danio migrate to temporary ponds and rice fields during the monsoon. They will spawn their eggs here as these waters are filled with plants that can be used as cover for the fry. The young fish will live in these waters until they disappear during the dry season.
In the wild, Danio rerio mainly eats small larvae and crustaceans. Feeding these fish in the aquarium is not very difficult. They will eat all types of food as long as it is meant for carnivores. Do keep in mind that providing a varied menu improves the health of these fish.
It is recommended to add lots of plants to your tank. This can provide enough cover for these fish. It allows them to keep on exploring the tank due to all the hiding spaces that are created. These fish like to explore new things and this helps to keep them satisfied. The Zebra Danio prefers a slight current in the aquarium.
Danio rerio makes a great specie for community tanks. These fish are very peaceful by nature and will not disturb other fish. However, do keep in mind that these fish are very active. This can be problematic for some fish species.
Breeding of these fish is relatively simple. They can even be seen spawning in a community tank. The eggs and fry, however, will normally be eaten in these types of tanks. In order to increase the yield, a breeding tank is recommended.
The breeding tank should have a setup to prevent the adults from eating the eggs. For this purpose, a special grid should be placed above the substrate. In this way the eggs will fall through the grid while the parents cannot reach them. Another option is to create a substrate of marbles. Filling the plants with a lot of live plants is another option. Taxiphyllum sp, is ideal for this purpose. The water in the aquarium should be filled half way with water that is slightly acidic to neutral. In addition will the temperature need to be increased.
When the aquarium is ready, the fish can be transferred to the breeding tank. When transferring the fish, pick the females that have the biggest belly. These are filled with eggs and thus ready to spawn. When placed in the tank, the fish should be get more food than normal. Once the fish are settled, one can begin with filling the tank. This should be done slowly with relatively cold water. Make sure the filling process takes several hours. This will mimic the monsoon. The next morning, the adults will start to spawn. When all the eggs are laid, the parents should be caught and transferred to another aquarium.
After 24-36 hours after eggs are spawned, they will start to hatch. A couple of days later the fry will be able to swim freely across the tank. At this time, feeding should begin. Initially, this should be done with the smallest food possible. Later on, when the fry has grown bigger, artemia nauplia can be fed as well.
As this species is relatively simple to maintain, it is not only popular for the hobby. Researchers like to use these fish as well. Furthermore, Danio rerio has been introduced in several countries to control the amount of mosquitoes. As a consequence, the Zebra Danio can also be found in several other countries such as the United States and Colombia.
Glowfish® is a genetically modified form of Zebra Danio. Genes from glowing jellyfish are added to the DNA of the Danio rerio. This causes them to start glowing themselves. These fish can be bought in several different colors. Keep in mind, however, that keeping and trading these fish is illegal in the European Union.
John de Lange