Zebra Danio Fish: Size, Group Size and Tank Mates

The zebra danio is Danio rerio, a small South Asian minnow named for the five even, horizontal blue stripes along its body (Wikipedia). It is one of the easiest aquarium fish, which PetSmart rates as a beginner fish, and it is also the zebrafish of biology labs: its genome of about 1.4 billion base pairs is fully sequenced, and it can regrow heart tissue and the hair cells of its lateral line (Wikipedia).

Telling males and females apart: males have gold stripes between the blue ones, while females have silver stripes and a larger, whitish belly (Wikipedia). Seriously Fish adds that mature females are rounder and slightly larger than males.

Up to 4 to 5 cm (1.6 to 2 in), though wild fish are usually 1.8 to 3.7 cm (Wikipedia). Seriously Fish gives a maximum of 50 mm standard length. They are small but very active swimmers, which is why tank length matters more than their size suggests.

At least six, and eight to ten is better. Wikipedia says they do well in schools or shoals of six or more, and Seriously Fish sets the minimum at 8 to 10. PetSmart's lower figure, the fish plus three or more others of its species, is the bare minimum for a shoal, not a target. In a larger group the fish spread their chasing across many others and show more natural behaviour.

The sources also disagree on tank size. PetSmart lists 10 gallons; Seriously Fish recommends a tank with a base of at least 90 by 30 cm (36 by 12 in), about 81 litres or 21 US gallons. For a proper group of 8 to 10, the larger figure is the safer one.

No. PetSmart rates them peaceful, and Seriously Fish calls them an extremely peaceful community fish that does not nip fins. What people notice is chasing inside the group, which is normal shoal behaviour and is spread out in a bigger group. Two cautions: adults eat hatchlings, including their own (Wikipedia), and their speed can stress very slow, long-finned fish at feeding time.

Seriously Fish lists tetras, livebearers, rainbowfishes and other small cyprinids as good companions, and PetSmart recommends community fish of similar size and temperament, plus top and bottom swimmers such as small catfish so the tank's levels are shared. Zebra danios also suit cooler community tanks: Seriously Fish gives 18 to 25 C (64 to 77 F), pH 6.0 to 8.0 and hardness of 5 to 20 dGH, and Wikipedia records wild fish in water from 16.5 to 34 C.

Feed a mix: they are micropredators that eat small crustaceans and insect larvae in the wild, and accept dried foods plus small live or frozen foods such as daphnia, brine shrimp and bloodworm (Seriously Fish).

Several colour forms are sold, all the same species:

• Leopard danio: spotted form, now recognised as a natural pigment mutation (Wikipedia; Seriously Fish)
• Long-finned and golden forms: selectively bred; the golden form is leucistic, not albino (Seriously Fish)
• GloFish danios: fluorescent transgenic fish, sold in the US since late 2003 (Wikipedia); Seriously Fish notes they are illegal in the European Union

Prices seen on 25 September 2026: PetSmart listed a zebra danio at $2.99. The GloFish online shop listed a single-colour 3-count set at $24.49, a 6-count set at $45.49, a mixed 5-count set at $42.99 and a mixed dozen at $95.99, in colours named Starfire Red, Sunburst Orange, Electric Green, Cosmic Blue and Galactic Purple. Check local rules before buying GloFish outside the US.

The zebra danio is the best-known member of Danio, a genus of small freshwater fish in the family Danionidae from South and Southeast Asia (Wikipedia). Wikipedia's article lists 34 recognised species. Most are marked with horizontal stripes, rows of spots or vertical bars, and some have two pairs of long barbels. They eat small aquatic insects, crustaceans and worms.

The name comes from Bangla: Wikipedia traces 'danio' to dhani, meaning of the rice field.

Danios you are likely to see in shops, with their scientific names from Wikipedia:

• Zebra danio, Danio rerio
• Pearl danio, Danio albolineatus
• Glowlight danio, Danio choprae
• Celestial pearl danio, Danio margaritatus

The fish sold as giant danios are no longer in Danio. Wikipedia explains that the genus was split in 1916 into larger Danio and smaller Brachydanio species, recombined in 1991, and the larger species then moved to the separate genus Devario. That is why care sheets for a giant danio and a zebra danio can differ, and why you should check the scientific name on the label.

No, the zebra danio is one of the easiest aquarium fish. PetSmart rates it Beginner and Peaceful, lists a 10-gallon minimum tank, and says it should be kept with three or more of its own species. It swims in the middle of the tank, so PetSmart suggests adding top and bottom swimmers of similar size and temperament. The group-size and tank-size advice earlier on this page, from Wikipedia and Seriously Fish, is more generous and is the better target.

Other danios vary. Celestial pearl and glowlight danios are much smaller fish, so check the needs of the exact species before mixing them with zebras, which are fast, active feeders.