What to Know About Zebra Danio

Medically Reviewed by Vanesa Farmer, DVM on January 09, 2023
5 min read

The zebra danio fish is also known as the zebrafish or striped danio. They are tropical, freshwater fish from Southern Asia. Scientists often use zebra danios for research, and they have become popular fish to keep in home aquariums.

Zebra danios have long, narrow bodies. If you look at them from the side, their body is wider in the middle and tapered at both ends. If you were to look at the fish head-on, you would see that their body is nearly flat. Zebrafish have five to seven horizontal stripes that run along the length of their bodies, extending onto their tail fins. They have bold stripes on the anal fin, which is on the underside of their body near the tail.

Danios are benthopelagic, which means that they feed at the surface, on the bottom, and in between. They will eat both swimming creatures and benthos (plants and animals that stay put on the bottom of a body of water). While most fish tend to hang out in one area of the aquarium, zebra danios will zip about on all levels of the tank.

As a fully grown adult, the average zebra danio reaches a total length (from the front of its head to the tip of its tail) of about 2.5 centimeters or 1 inch. The longest zebrafish in recorded history grew to 6.4 centimeters or about 2.5 inches.

Zebrafish are social creatures that like to shoal or swim together in a group. This is different from schooling, when fish swim together in the same direction, moving and changing course as a group. Shoaling means fish cluster together in the water. 

Within a shoal, there is a social hierarchy. To establish dominance — a position of power in the group — a zebra danio will temporarily become aggressive. This behavior can include chasing and even biting other fish.

Get at least five zebra danios for your aquarium so they can shoal. Too few fish or too little space can stress these fish. The minimum aquarium size for zebrafish is 10 gallons, as they are active and need room to zip around. If you have other fish species in the tank, make sure you've got about 1 gallon of water for every inch of fish.

In the wild, zebra danios seem to live about a year. In an aquarium, they live 3 to 5 years on average. Some zebra danios have lived in aquariums for as long as 5.5 years.

Zebra danios like a tank temperature of 26 C (around 79 F). They can tolerate changes in temperature as long as their water stays between 22 and 30 C (about 72 to 86 F). Zebra danios also need their water to have a pH between 7.0 and 8.0, and they prefer a narrower range of 7.0 to 7.4 pH.

Zebrafish are diurnal, meaning they are more active during the day and sleep more at night. Too much light can keep them from sleeping. Light the tank for 14 hours out of every 24, and minimize the light around your aquarium for the other 10 hours.

Zebra danio fish tank mates should be freshwater fish that are comfortable in the same temperature and pH ranges zebrafish prefer. Plan ahead of time how you will feed both types of fish. Two different species of fish may have very different diets. 

Fish that eat the same diet may fight over food if they don't have enough food or space. Zebrafish sometimes nip the fins of other fish, so have a backup plan in place in case your zebra danios are too hard on the new fish.

In the wild, zebrafish eat worms, larvae (insects in an immature stage of development), and small crustaceans.

As pets, zebra danios aren't picky eaters. However, they especially like fresh vegetables and live (or frozen) invertebrates.

Feed zebra danios twice a day. Start with small amounts until you learn how much your fish need. You want all the fish to eat but the food to be gone in about 5 minutes. Offer a variety of foods, at least two or three types. Good choices include:

  • store-bought fish flakes
  • ground cichlid pellets (higher in protein than most fish food)
  • brine shrimp or brine shrimp larvae
  • tubifex worms
  • crumbled yolk from hard-boiled eggs

The name danio comes from "dhani," a Bengali word meaning small minnows. Bengali is a language spoken in Bangladesh, one of the countries where zebra danios live in the wild. Zebra danios are also native to India, Pakistan, Nepal, and Myanmar. They swim in standing water, especially in rice fields, and in slow-moving water like small streams and ditches.

Scientists choose zebra danios for cancer research because their young are transparent (clear). This makes it easy for researchers to see what's happening with a fish's organs as it grows. As they get older, the fish get their stripes and are no longer see-through. To get around this, scientists have learned how to make some of the zebrafish's organs glow under ultraviolet (UV) light so they can continue to watch the fish's development through all life stages.

The cells of zebrafish and those of humans are similar enough that scientists test medications and other treatments on zebrafish. Adult zebra danios have the ability to regrow injured tissue. For instance, a zebrafish can regrow a tail fin in about 30 days. They can also regenerate their kidney, spinal cord, and retina (part of the eye). Researchers are studying these fish to understand how animals regrow tissue after injury.

The zebra danio can repair its own heart by making new heart muscle cells to replace damaged ones. Scientists are studying zebra danios in the hopes that they will learn how to help people who've had heart attacks.