Freshwater Fish

Danio Zebra [Danio Rerio]- Care Guide

If you’ve ever wondered why Danios are such a popular choice for freshwater aquariums, wonder no more. These zebra-striped fish are beautiful and hardy, and are one of the easiest aquarium species to care for and breed. Ideal for novice and experienced aquarists alike, let’s explore the playful Zebra Danio!

Zebra Danio Overview

The Zebra Danio (Danio rerio) is a mainstay in the aquarium trade and has been for many decades. I’d hazard a guess that there are few aquarium stores in the United States that don’t have at least one type of zebrafish for sale. Let’s talk about why these social fish are such a popular choice for freshwater tanks.

Scientific name denmark river
Common name Zebra Denmark, Striped Denmark, Zebrafish
level of care Easy
size range Up to 2 inches long; average size is 1.5 inches at maturity
Diet Omnivore; In the wild, they eat small insects and eggs, algae, crustaceans, and worms.
Exercise Active, curious schoolchildren in larger groups (15+)
Temper Playful and very social
Minimum tank size 10 gallons
Temperature range 64 to 77°F

Danio natural history

Zebra danios are small freshwater fish native to South Asia. Originally found in various parts of India, Pakistan, Bangladesh, Nepal, and Bhutan, the striped danio has also been released into the wild (both deliberately and by accident) in Colombia, Malaysia, and parts of the United States. Danios are:

  • Members of the great family of cyprinids or minnows.
  • Omnivorous and feed mainly on zooplankton, phytoplankton (including algae), small insects and larvae.
    • They will also consume small crustaceans and worms if their preferred foods are not available.
  • Tolerant of a wide range of habitats and water conditions.
    • Wild populations exist in streams, rivers, lakes and even almost stagnant ditches and rice paddies.
    • Usually found in shallow water shaded by aquatic vegetation or overhanging with a substratum filled with sandy or silty pebbles.
  • “Danio” derives from the Bengali name Dhani, which means “of the rice fields”.

The zebrafish, as it is also called, is only one of 23 currently recognized danio species. Other popular aquarium varieties include Pearl Danio (Danio albolineatus), Celestial Danio Zebra (Danio margaritatus), and Emerald Dwarf Rasbora (Danio erythromicron).

Importance for science and research

The zebrafish was first described in India in 1822 by the Scottish physician and explorer Francis Hamilton. Initially dismissed as a worthless fish, they have since become a model species for scientists studying everything from the genetics of neural development to cancer, and have even been sent into space!

This extensive research has led to the zebrafish being one of the best understood species on the planet:

  • His DNA was fully sequenced in 2001 and continues to be studied in more than 600 laboratories around the world.
  • Their easy breeding habits and large, transparent eggs make them ideal for laboratory experiments.
  • They share around 70% of their genetic material with humans, making them ideal for studying diseases such as diabetes and muscular dystrophy, and for use in developing new drugs and treatments.

Danio’s size and appearance

How big are zebra danios? They are usually sold as juveniles about 0.5 to 1 inch long, with the size of a mature zebra danio usually maxing out at about 1.5 to 2 inches. Pond fish can grow larger than danios kept in aquariums.

The zebrafish is known for the five iridescent dark blue stripes that run down its body on both sides from its head to the tip of its caudal (tail) fin. Their bodies are spindle-shaped (fusiform) and their mouths are upturned. Its natural background color is usually a subtle silver to gold stripe.

Sexual dimorphism also known as gender differences

Slender zebra danio males are torpedo-shaped and often have subtle gold stripes between the zebra stripes on their bodies. Silvery-white females have a rounder, plump body with a white belly and silver stripes instead of gold. They also have a prominent genital papilla, or bent tube, just in front of their anal fin.

Varieties and color variations

While the wild-type zebrafish is a popular choice, there are many other interesting varieties available in the aquarium and research laboratory trade. Naturally occurring mutations, artificial selection by breeders, and the increasing use of genetic modification have given rise to several unique morphs, including:


  • Natural albino zebra danios lack pigmentation and are whitish to pinkish in color.
  • The rarer Golden Danio Zebra has a gold ground color and silver-white stripes.
  • There are also genetically modified zebrafish that glow under fluorescent light. These GloFish Danio Zebra come in green, orange, pink, blue and purple colors.
  • Transparent Danio Zebras were created by scientists for research and are not yet commercially available (but may be soon). They lack all pigmentation, so you can see through their skin and look at their internal organs.
  • There is also a Long-finned Zebra Danio, which has enlarged and elongated dorsal, pectoral, pelvic, anal, and caudal fins.
  • Danio Lifespan

    In the wild, zebrafish are considered an annual species and typically only live for about a year. But when well cared for, you can expect the fish in your aquarium to live between 2 and 5.5 years.

    behavior and temperament

    What is the typical behavior of zebra danios in an aquarium? They are live, active and social fish that prefer to live in large groups. It is best to have at least 5 baits, and schools of 15 or more are ideal. When kept alone, these fish are shy and spend most of their time depressed and hidden.

    Zebrafish develop a social hierarchy through play and fishing (swimming in loose groups). They often bite and chase harmlessly. Zebras use all parts of their aquarium, but prefer to hang out in the top and middle sections. They prefer to swim in the open shady areas of their tank.

    In terms of temperament, these fish generally get along with other species of similar size and shape from peaceful communities, but often prey on slow-moving, long-finned fish. While they safely form hierarchies through their non-aggressive play, they may stress or injure slower fish while nipping at their fins.

    How to Care for Your Danio Zebras

    Zebrafish are one of the easiest species to care for in an aquarium and are also a good choice for outdoor ponds. This makes them an ideal choice for new fish keepers and for single species or peaceful community tanks.

    Tank Configuration and Habitat Requirements

    Zebrafish are not very picky about their specific setups and can usually be accommodated in most tanks without much fuss.

    aquarium size

    What is the best tank size for zebrafish? It depends on how many fish you want to have in your school. You can keep a small group of 5 danios in a 10 gallon aquarium, or a school of 25 in a 50 gallon tank. As long as you provide them with a good 2 gallons per fish and avoid groups of less than 5, your fish should be fine.


    In the wild, zebrafish live in bodies of water that are silty or have sandy bottoms. Truth be told, in an aquarium, you can use whatever substrate you prefer. These fish will not be harmed by regular aquarium gravel, although sand is a more natural choice for them. They really do stand out beautifully in a tank with a mix of dark sand and pebbles.

    Water and temperature parameters

    What kind of temperatures and water conditions do zebrafish prefer?

    • They do well in a wide range of temperatures from 64 to 77°F as long as you stay consistent and only change slowly.
      • Aquatic heaters are helpful, but you may not need one for your zebra danios if your tank doesn’t fluctuate much and stays consistent within a couple of degrees.
    • They are not particularly sensitive to water hardness as long as it is between 5 and 12 dGH.
    • Zebrafish prefer a pH between 6.0 and 8.0.

    Filtration, aeration and lighting

    It is best to have a good filtration system in your zebrafish tank to keep the water clear and clean and to help maintain oxygen levels in the water. A simple internal filter may suffice for a nano tank, while a canister or HOB system would be better for larger setups.

    While wild zebrafish can often be found in stagnant water, it’s best to provide your fish with a gentle current and plenty of circulation to prevent other problems with your tank (such as algae blooms). I have seen my zebra playing in my filter outlets and they also like to swim through bubbles so consider adding an air stone.

    To recreate their natural habitat, it is best to provide zebrafish with open, shady areas to move around. You can use taller plants like Amazon Swords and Java Fern to create these shady spots for your zebrafish. They may avoid playing in brightly lit areas away from decor and plants.

    Plants and Decorations

    The ideal zebrafish tank would have at least some live plants, but you can also choose to decorate with plastic plants if you prefer. They also enjoy exploring decorations, especially swamp driftwood.

    But they aren’t really sensitive to your decorations, so choose the decoration that works best for your tank and community. Zebrafish do not like a bare tank and tend to be more aggressive when they don’t have a lot of plants and decorations to break up their habitat.


    Maintaining a danio tank is not difficult and does not require a lot of time or effort. The key is to adopt a regular routine for water changes and filter maintenance. Poor hygiene can cause fish stress and shorten their lifespan, and can increase the chances of algal blooms and disease in your tank.

    feeding guide

    What do zebrafish eat and how often should you feed them? As omnivores, they enjoy both plant and animal foods. I usually feed my zebrafish 6 out of 7 days a week, with one fast day without food. I offer them their main diet five times a week and treat food instead of their food once a week.

    • It is best to feed them a high quality omnivorous commercial flake food as their main diet, offering as much food as they can consume in about 3 minutes.
    • You can also offer them occasional flakes of seaweed.
    • For treats, you can offer them fresh/frozen/dried brine shrimp , bloodworms, or mosquito larvae.
    • They also enjoy blanched vegetable delicacies like spinach, cucumbers and zucchini.

    Feeding of breeding colonies and fingerlings

    For breeding zebrafish, it is best to feed them brine shrimp, Daphnia eggs, and bloodworms for a few weeks before spawning. Newly hatched zebrafish fry do best with a mix of powdered omnivorous food and fresh brine shrimp fry until they are large enough for normal food.

    tank mates

    What are the best tank mates for zebrafish? You have many options, including small tetras like Neon, Cardinal, Rummy Nose, and Emerald. They make good choices for communities with Gourami, Cherry, and Gold Barbs. You can also house them with other types of danios.

    Zebrafish also work for tanks with Nerite, Zebra, or Assassin snails. You can keep them with small freshwater invertebrates like Ghost or Cherry Shrimp, or aquatic amphibians like the African Dwarf Frog. Other possibilities include Cory Cats, loaches, and the Upside Down Catfish.

    Species to avoid

    Avoid keeping zebras with long-finned or slow-moving fish like Sailfin Mollies, Fancy Guppies, Fancy goldfish, or Bettas, or any large or aggressive species like Tiger Barbs or Red-Tailed Sharks. If your zebras are acting aggressive towards the community, try dividing up the tank with more decorations and live plants.

    Danio Breeding Overview

    It is incredibly easy to breed zebrafish and they are a great choice for first time fish keepers. You will need several small breeding tanks with heaters, sponge filters, and air stones. Separate your fish into tanks by gender for a few weeks and raise the water temperature to 71 to 80°F to signal that it is time to spawn.

    After two weeks on a high-protein diet, your female fish should start to look plump and round. It’s time to transfer them to the spawning tank. Add 2 males for each female. You should see clear eggs at the bottom of her tank within 24 hours. Infertile eggs are not transparent and instead appear white.

    Once the adults have spawned, return them to their home tanks or they will eat the hatching fry. Your baby fish should hatch in 3 days and will be very small and transparent at first.

    health concerns

    Zebra danios are usually healthy and hardy fish, but they are susceptible to common aquatic diseases like ich, so the hygiene of your tank will play a big part in the overall health of your school. Stressed fish are more likely to get sick, after all, as stress depresses their immune systems.

    Zebrafish are also highly susceptible to a chronic bacterial infection called mycobacteriosis, which is especially common in laboratory colonies:

    • This disease causes fish to be lethargic, anorexic, and develop inflammation and ulceration of the skin and fins.
    • Sick fish may develop dropsy (edema or swelling of the body), nodules in their internal organs, and may even have deformed muscle and skeletal development.
    • This is a zoonotic disease and you can potentially become infected through any open wounds on your skin.

    There is no treatment for mycobacteriosis as it is usually related to poor animal husbandry practices. Antimicrobial drugs don’t seem to have much of an effect, and an outbreak usually results in colony loss. This is best avoided by keeping water quality high and quarantining new fish before adding them to your tank.

    What Supplies Do You Need For A Zebrafish Tank?

    Here’s a quick shopping list of the supplies you’ll need for an ideal danio tank fit for a bank of 10:

    • 20 gallon aquarium with hood/cover and lights.
    • Internal filter, HOB or canister.
    • Sandy substrate with a mixture of boulders and smooth stones.
    • Air pump and air stone or bubbler device.
    • Live or plastic plants and decoration; Swamps and sticks/branches are especially suitable.
    • A heater, if the temperature in your home is variable or varies by more than a few degrees each day.
    • A bottle of water conditioner to remove chlorine or chloramine from tap water.

    To feed and care for your zebrafish, you will need:

    • A high quality commercial omnivorous flake diet.
    • These are brine shrimp, bloodworms, Daphnia eggs, and/or mosquito larvae.
    • Seaweed flakes and fresh blanched vegetables for occasional treats.
    Common name (species) Zebra Denmark (Denmark rerio)
    Family Cyprinids
    Source South Asia in India, Pakistan, Bangladesh, Nepal, and Bhutan
    Diet and feeding Omnivore; Primary diet of fish flakes, supplemented with fresh/frozen brine shrimp, bloodworms, seaweed flakes and blanched vegetables
    level of care Easy
    Exercise Very active, curious species and school in large groups (15+)
    Temper Playful and very social; they often chase and bite each other harmlessly
    tank level Mostly high and mid levels, but also explores the bottom
    Minimum tank size 10 gallons (2 gallons per fish)
    Temperature range 64 to 77°F
    Hardness of water 5 to 12 dGH
    pH range 6.0 to 8.0
    Filtration / Flow Rate Prefers well-filtered water with a slight stream.
    Breeding Egg layer; Ideal species for first time breeders and very easy to induce spawning in a breeding tank.
    Compatibility It adapts well to many other peaceful fish of similar size that prefer the same conditions. Avoid staying with large or aggressive fish that can attack them, or slow swimmers with long fins that can get pinched.
    Is it ok for planted tanks? Ideal for planted tanks


    Zebrafish may be common, but they are anything but boring! I hope you’ve enjoyed this guide and we’d love to hear any questions or comments you may have about these beautiful zebra danios. You can leave a comment below or join us and our community of aquarium hobbyists on our social media pages!

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