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.
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Habitat in the wild
The zebrafish, scientifically known as Danio rerio, belongs to the Cyprinidae family. This family is commonly referred to as the “carp family” or “minnow family.” Zebrafish are a popular freshwater fish species in the aquarium trade and have also gained significant importance as a model organism in scientific research, particularly in developmental biology and genetics.
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 zebrafish (Danio rerio) is native to the freshwater habitats of Southeast Asia, particularly in countries such as India, Bangladesh, Nepal, and Myanmar. In its natural habitat, zebrafish can be found in slow-moving or stagnant waters, including ponds, rice paddies, ditches, and small streams. These waters often have a dense growth of aquatic plants, providing shelter and breeding sites for the fish.
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.
In the wild, zebrafish feed on a diet of small invertebrates, zooplankton, and insect larvae, and they are known for their striking blue and silver stripe pattern, which serves as camouflage in their natural surroundings. This distinctive appearance, along with their adaptability, has made them a popular and iconic species in both the scientific and aquarium communities.
Description
Size
How big do zebra danios get? The size of a zebrafish can vary, but they typically reach an adult length of about 2 to 2.5 inches (approximately 5 to 6.5 centimeters). This size makes them relatively small and well-suited for community aquariums, where they are popular due to their active behavior, striking appearance, and ease of care. Keep in mind that individual zebrafish can vary slightly in size, and proper care and diet can influence their growth.
Lifespan
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.
Coloring
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.
Types of danios
There are several recognized variations and color morphs of zebrafish (Danio rerio), each with its own unique appearance. Here are a few notable types:
- Wild-type Zebrafish: This is the most common and natural form of zebrafish, characterized by its silver body with horizontal blue stripes.
- Leopard Danio: This variety features spots on its body in addition to the usual stripes. The spots may be black or dark brown, creating a “leopard” pattern.
- Longfin Zebrafish: These zebrafish have longer, flowing fins compared to the standard wild-type. This trait is a result of selective breeding.
- Albino Zebrafish: Albino zebrafish lack pigmentation, giving them a pale, almost translucent appearance. Their eyes appear red due to the absence of pigments.
- GloFish Zebrafish: These are genetically modified zebrafish that express fluorescent proteins, creating vibrant colors when exposed to certain light. There are several GloFish varieties, including Electric Green, Cosmic Blue, and Sunburst Orange.
It’s essential to note that the aquarium trade and selective breeding have led to the development of various color morphs and patterns. These different types of zebrafish can add diversity and visual appeal to aquariums, but it’s essential to ensure proper care for each type based on its specific needs.
| Characteristic | Description |
|---|---|
| Scientific Name | Danio rerio |
| Family | Cyprinidae (Carp family) |
| Native Range | Southeast Asia (India, Bangladesh, Nepal, Myanmar) |
| Habitat | Freshwater: Ponds, rice paddies, ditches, small streams |
| Size | Typically 2-2.5 inches (5-6.5 cm) in length |
| Lifespan | Average 2-3 years (can vary with care and environment) |
| Coloration | Silver with distinctive horizontal blue stripes |
| Behavior | Peaceful, active, schooling fish |
| Diet | Omnivorous – small invertebrates, zooplankton, insect larvae, and flake/pellet foods |
| Aquarium Suitability | Popular in the aquarium trade; hardy and adaptable |
| Breeding | Egg-scattering species, relatively easy to breed in captivity |
| Use in Research | Widely used as a model organism in genetics and developmental biology studies |
| Importance | Significant in genetics research, aquaculture, and the aquarium trade |
Zebrafish as a model organism
Zebra danio 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.
Zebra danio 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 zebra danio 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.
Tank size
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.
Water parameters
Danio rerio are relatively hardy and adaptable freshwater fish that can tolerate a range of water parameters, making them suitable for a variety of aquarium setups. However, to ensure their well-being and minimize stress, it’s essential to provide them with stable and appropriate water conditions.
Here are the recommended water parameters for zebrafish:
- Temperature: Zebrafish prefer a temperature range of 74-78°F (23-26°C). This temperature range is suitable for most tropical community aquariums. 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 74-78°F (23-26°C). In this case, zebra danio are more disease-resistant.
- pH: The optimal pH range for zebrafish is around 6.5 to 7.5. They can tolerate slightly acidic to slightly alkaline conditions.
- Water Hardness: Zebrafish can adapt to a moderate level of water hardness. A general hardness (GH) of 5-15 dGH and a carbonate hardness (KH) of 3-8 dKH are suitable.
- Ammonia, Nitrite, and Nitrate: It’s crucial to keep ammonia and nitrite levels at zero, as these substances are toxic to fish. Nitrate levels should be kept below 20-30 ppm through regular water changes.
- Water Quality: Good filtration is essential to maintain water quality. Adequate filtration helps remove waste, ammonia, and nitrites from the water. Regular water changes (about 25-30% of the tank volume every 1-2 weeks) are also crucial for maintaining a healthy environment.
Remember that sudden changes in water parameters, such as temperature or pH, should be avoided, as these can stress the fish. When introducing zebrafish to a new aquarium, it’s a good idea to acclimate them slowly to the tank’s water conditions to prevent shock. Monitoring water parameters regularly and maintaining a consistent environment will help ensure the health and well-being of your zebrafish.
Tank setup: decorations and plants
The zebra danio 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.
Filtration
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.
Diet
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.
Tank mates
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.
Here are some suitable tank mates for zebrafish:
- Harlequin Rasboras (Trigonostigma heteromorpha)
- Neon Tetras (Paracheirodon innesi)
- Ember Tetras (Hyphessobrycon amandae)
- Glowlight Tetras (Hemigrammus erythrozonus)
- Black Neon Tetras (Hyphessobrycon herbertaxelrodi)
- Cardinal Tetras (Paracheirodon axelrodi)
- Rummy Nose Tetras (Hemigrammus rhodostomus)
- Dwarf Gouramis (Trichogaster lalius or Trichogaster chuna)
- Sparkling Gouramis (Trichopsis pumila)
- Celestial Pearl Danios (Danio margaritatus)
- White Cloud Mountain Minnows (Tanichthys albonubes)
- Dwarf Rasboras (Boraras spp.)
- Endler’s Livebearers (Poecilia wingei)
- Guppies (Poecilia reticulata)
- Platies (Xiphophorus spp.)
- Corydoras Catfish (Corydoras spp. – pygmy cory, panda cory, adolfoi catfish)
- Otocinclus Catfish (Otocinclus spp.)
- Bristlenose Plecos (Ancistrus spp.)
Gender differences: male vs female
Distinguishing between male and female zebrafish (Danio rerio) can be challenging, especially in young fish. It is possible to tell between the zebra danio 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.
However, there are some subtle differences that can become more apparent as the fish mature. Here are a few characteristics that can help you differentiate between male and female zebrafish:
- Size: 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.
- Body Shape: In general, female zebrafish tend to have a slightly rounder and plumper body shape, especially when they are carrying eggs. Male zebrafish often appear slimmer and more streamlined.
- Coloration: Pay attention to the zebra danio coloring intensity. The stripes on the female bodies are paler and less visible, while the males are brightly colored and opalescent. While both male and female zebrafish have the characteristic silver body with blue horizontal stripes, some male zebrafish may exhibit more intense colors, particularly during courtship or when displaying to females. This difference is more noticeable in certain color morphs, like the longfin zebrafish, where the coloration of males can be more vibrant.
- Anal Fin: One of the more reliable ways to differentiate between male and female zebrafish is to observe the shape of the anal fin (ventral fin located near the tail). In males, the anal fin is usually more pointed and has a slightly elongated appearance, while in females, the anal fin is generally more rounded.
- Behavior: During breeding or courtship, male zebrafish may display more intense chasing and fin-flaring behaviors, while females might show less aggressive behavior.
It’s important to note that these differences may not be readily apparent in juvenile zebrafish, and it might be easier to distinguish between males and females as they mature and develop reproductive characteristics. If you’re interested in breeding zebrafish or want to ensure a balanced community, it’s helpful to observe their behavior and physical characteristics over time.
Breeding
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 zebra 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 zebra danio, 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 zebra danio 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.