Zebra danio (Danio rerio) is a freshwater fish from the Cyprinidae family. It is a small, nimble, and not demanding fish. In the article, you will find information on keeping zebra danio, its compatibility with other fishes, and how it differs from glofish danio.
Habitat in the wild
This fish kind was first described in 1822 by Francis Buchanan-Hamilton, a famous scientist who significantly contributed to studying the nature of India. As a result of the regular revision, the kind was classified as Danio genus, and nowadays correct scientific name of the kind is Danio rerio.
The fish dwells in rivers and streams in Pakistan, India, Bangladesh, Nepal, Myanmar, and Bhutan. Zebra danio inhabits rivers, channels, ponds, rivers. The place where the fish dwells to a large extent depends on the season. The adult species in large numbers can be encountered in puddles that appeared during the dry season and in flooded rice fields, where the fish feeds and spawns. After the rain season, the fish gets back into rivers and large water basins. In the wild, zebra danio feeds on insects, seeds, and zooplankton.
Here things are quite complicated since fish coloring and fins length vary significantly within many species. However, all of them come from the same fish kind, have similar behavior, and require the same care.
How big do zebra danios get? Fish size about 4 cm (1.6 in) long. It is a fish with a fusiform silvery body with bright blue stripes. Young species have short fins, but in time, they grow longer and form a veil (there are also long-finned species). Fins edges may be yellow. There is a pair of tiny downward barbels in the corners of the fish mouth.
Zebrafish as a model organism
Danio fish is a popular model object in biology to study embryogenesis and genes of vertebrates. This is because the fish eggs develop quite fast. It takes only three days, and the embryos themselves are rather large and enduring, which allows performing various manipulations with them. Zebrafishes became the first genetically modified fish. The story of the famous fluorescent fish GloFish began with Danio.
Danio rerio was suggested by American molecular biologist George Streisinger as a model organism to study embryogenesis and genes function of vertebrates. The importance of this model organism was proven by many genetical researchers.
Zebra danio is one of few fish kinds used in experiments in space. They were taken to International Space Station (ISS) and Salyut 5.
When studying the biology of Danio rerio development, it has several advantages if compared with other vertebrates. Its embryo develops fast, and it takes just 3 days to pass the stage from an egg to a larva.
There is significant potential in using zebra danio as a model organism for screening potential medicines due to the speed and convenience of working with it. Despite a rather low similarity between fishes and humans, many systems of these organisms, namely, the cardio-vascular system, interact with low-molecular composition in the same way.
Consistent results can be obtained when studying the pharmacokinetics and toxicological characteristics of various medicines. Genetic engineering methods may help obtain new breeds of Danio rerio that will specifically imitate various human diseases.
Difficulties in keeping
Zebra danio is a good-looking and unpretentious fish, a perfect choice for beginning aquarists, and an excellent choice for a community tank. Zebrafish eats any food that you give it. The fish easily stands various tank water parameters, and it can live even without heating the tank water.
Care and keeping in a tank
This fish is amazingly not demanding, capable of living in various tank conditions. However, they have some preferences you should take into account.
The zebra danio dwells mainly in upper water layers. Due to this fact, you won’t have to install additional aeration on the tank. A long tank is preferable for this fish since it is very active and likes chasing its tank mates.
If the zebra danio feels endangered, it can jump out of the water right into the air. Therefore, to prevent your pet’s death, the tank should always be covered with a lid. The optimal distance from the water surface to the tank lid is about 5 cm (2 inches) to make sure that if the fish jumps out, it won’t get hurt because of hitting the firm surface of the lid.
|Scientific Name||Danio rerio|
|Common Names||Zebra danio, zebrafish, zebra fish|
|Ease of keeping||Easy|
|Lifespan||3 years and more|
|Tank size||40 liters (10 US gallons) and more|
|Tank type||Community of small fishes|
|Temperature||21-25 °C (70-77 °F)|
|Water hardness||6–15 dGH|
|Size||Up to 4 cm (1.6 in)|
This is a small fish which means that it doesn’t live long. However, provided with proper conditions, zebra danio can live about 3-4 years.
Danio rerio lives in groups. It’s better to keep them in a school of 5 species and more. This way, the fish is more active and less prone to stress. For such a school, a tank of 40 liters (10 US gallons) capacity. Though, the more, the better – since the fish needs space to swim.
Technically you may call the fish a cold water dweller (it lives in the water about 18-20 °C (64-68 °F). However, it has adapted to various tank parameters because the fish is successfully bred in large numbers. Zebra danios can easily stand living in tanks without water heating at the temperature range from 18 to 25 °C, and they stand short-term water temperature decrease to 15 °C and raise to 30 °C.
But still, it’s better to maintain the tank water temperature around 21-25 °C (70-77 °F). In this case, zebrafish are more disease-resistant. Optimal water hardness is 6-15 dH, and pH about 6.5-7.5. For zebrafish to feel good, it is desirable to renew up to 15% of the total water amount with fresh water every week and control the water hardness and acidity.
Tank setup: decorations and plants
The fish has no specific requirements, neither to tank decorations nor to plants (they don’t touch these at all). The only thing is that the fish is active, and it requires space to swim. Therefore, you should put long-stalked plants along the tank walls, and the rest of the tank space is for zebrafishes to swim.
Danio likes clean water, so you should take care of proper filtration in the tank as well as aeration. However, they are so undemanding, and they can even live without these.
Wild zebra danio has a rather diversified diet. They eagerly eat small insects and maggots they find in the water, as well as small seeds falling from the plants.
Zebrafish prefer eating food from the water surface. However, if the food starts drowning, the fish can catch it under the water, but it almost doesn’t eat the food from the tank bottom. The fish is not demanding. It eats all types of live, frozen, or artificial food.
Fist two types of food sometimes can’t completely meet zebra danio dietary needs since they aren’t balanced enough and don’t contain vitamins the fish need. Therefore the best choice is to select quality artificial food. They prefer feeding on the water surface, so the food must stay on the surface for a long time.
You should feed the fish several times a day with a portion that it can eat in several minutes.
This is a perfect fish for a community tank. It gets on well both with related species and most other tank fishes. You can keep it with small and peaceful fish (not large ones like oscar fish, blood parrot, convict cichlid). For example, bettas, guppies, neon tetras, ember tetra, honey gourami, platy, swordtail are good tank mates for zebra danio.
Any peaceful catfishes (like panda cory, bristlenose pleco) will also be a good choice of the tank mates since they have different feeding niches: catfishes are bottom dwellers while Danio prefers swimming near the water surface. Even bettas don’t pay much attention to these constantly swimming neighbors.
Are zebra danio and goldfish compatible? My answer is no, even though the fish prefers colder water than other tropical fishes. The thing is that goldfishes grow to become quite large, and they are always hungry, so that they may be dangerous for zebra danio. While adult angelfishes won’t be able to swallow zebra danio, despite they’d love to. I’d be careful when keeping zebra danio together with any of these kinds.
Are zebra danios fin nippers? Danio rerio chases each other, but such behavior doesn’t demonstrate aggression. This is how they live in a school. They don’t hurt each other and don’t harm other fishes. It is better to keep at least 5 fish in a tank. Such a school will have its own hierarchy, and it is less prone to stress.
Gender differences: male vs. female
It is possible to tell between the male and female only for adult fish species. Young fish species are not formed completely, so both males and females are very much alike. If the fish gender is important for you, you must buy only the adult fish species.
The most reliable criterion to define the fish’s gender is its size. Look at the fish school and try to compare them. The females are larger as a rule, and they have a more rounded abdomen. The males are more streamlined but a bit smaller in size.
This peculiarity of the fish’s gender dimorphism is connected with the ability to lay eggs, which depends directly on the female fish size.
Pay attention to the fish coloring intensity. The stripes on the female bodies are paler and less visible, while the males are brightly colored and opalescent.
You will have to separate the zebra danio couple, make the tank water temperature higher and feed the fish intensively. The rounded body of the female fish will show you when it is ready to spawn.
Use a small volume with a glass bottom as a spawning tank. Experienced aquarists do not recommend putting sand on the bottom since you won’t see how the fish lays eggs in this case. However, it is obligatory to put some small-leaved plants on the bottom (java moss, for example). Take the water for the spawning tank from the community tank, but before pouring it through a siphon and add some fresh, reach in oxygen water into it.
Don’t make the water level high in the spawning tank – 8 cm of water level is more than enough. This way, you’ll have a 4 cm of water layer above the moss. Put one female and two male fish into the tank in the evening and, if possible, put the volume near the window.
It happened that the tank water temperature doesn’t play any significant role in this process. It was observed that danio easily spawns both at the temperature of 25 °C and 17 °C. During the night, the fish will get used to the new tank conditions, and in the morning, when the plants start producing oxygen, and the volume will be well lighted, they will start spawning.
I’ve never seen the zebra danio moving so abruptly in a tank than that of the danio mating game. The male fish try as hard as they can to make the female lay the eggs. This process lasts about 5-6 minutes without rest, and the spawning itself seldom lasts longer than an hour.
How many eggs does the female fish lay at one time? This is a rhetorical question since the number of eggs is directly proportional to how ready for spawning the female is and its size. I can only give you a range of possible eggs number for one spawning: it is from 50 to 400 eggs.
You may get the offspring from just a couple of fish, though as experience showed, in this case, the eggs are not fertilized enough. That’s why most aquarists tend to use 2 males and 1 female fish for spawning. If your spawning tank is big enough, you surely can put several fish couples there.
Once the fish finish laying eggs, remove them from the tank and put males and females separately. In a week or two, you should put them together to perform spawning one more time. Otherwise, the eggs may get too old, and there will be no juveniles; sometimes, it happens that the female fish just won’t be able to lay eggs anymore at all.
I often saw complaints of some aquarists on the forums that zebra danio lay awful eggs or don’t lay eggs at all. Both can be explained by the fact that the fish didn’t receive proper care. The fish that was supposed to spawn was likely kept in warm water and fed intensively for a long time. This caused over ripping of the fish eggs, and they ‘got old’ then. The fish won’t lay the eggs if they are old. To avoid such unpleasant surprises, keep the fish you want to spawn in the water which temperature is not higher than 19 °C in the winter season and don’t feed them too much.
The eggs incubation time directly depends on the temperature profile in the tank. If the temperature is 28 °C, juveniles will appear in a day and a half, but at 16 °C, the offspring will hatch in 2 weeks.
Once the larvae hatch from the eggs, it sticks to the tank plant leaves and tank walls and hangs like there. At first, you should feed it with infusorian, and as the larvae grow, some larger-sized food can be added to its diet.
If you keep the tank water temperature at about 27 °C, provide good aeration and high feeding, the zebrafish becomes reproductive at three months. The lower the temperature is, the slower the fish develops.