How many zebra danio should I keep?

Minimum 6; for community-tank stability and proper behavior, the high end of the range is more reliable. Solo or paired individuals of schooling species typically hide and stop displaying normal behavior.

What tank size do I need?

Realistic minimum is 20 gal long. Smaller tanks technically house the species but compress the social and territorial dynamics in ways that show up as stress over time.

What water parameters does this species prefer?

Temperature 64–77°F (18–25°C), pH 6.5–7.5, GH 5–19 dGH. Tank-bred commercial stock typically tolerates a wider range than wild-type fish, but parameters in the middle of the listed range produce the most consistent behavior.

Zebra Danio Care — Cold-tolerant active mid-water darter; the laborat

Scientific name

Danio rerio

Origin

South Asia (India, Bangladesh, Nepal)

Adult size

1.5–2 in (4–5 cm)

Lifespan

3–5 years

Min group / structure

6 (8+ to prevent fin-nipping)

Min tank size

20 gal long

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Hi, I'm the FishTankMath assistant. I answer questions about aquarium math (volume, water changes, stocking, dosing), how the calculators on this site work, and common freshwater-fishkeeping basics. I'm not a veterinarian — I can't diagnose or treat sick fish. For emergencies or sick livestock, talk to an aquatic vet or your local fish store.

Overview

Among the hardiest community species in the hobby — temperature-tolerant, water-parameter-flexible, and active enough to add real movement to a planted tank. Below 6 in a group, they fin-nip; in groups of 8+, aggression channels into the school instead.

Behavior and group dynamics

Active, fast swimmers that cover the entire tank but spend most time in the upper third. Group dynamics are critical — solo or paired zebra danios get bored, get bossy, and start nipping the fins of slower tank mates. Groups of 8+ keep the energy contained within the school.

Tank requirements

A 20-gallon long with strong horizontal swim space — they're sprinters, not aquascape ornaments. Cooler-tolerant than most tropicals; can be kept at room temperature (low 70s) without a heater in many cases, which makes them appealing for beginner setups.

Temperature: 64–77°F (18–25°C).
pH: 6.5–7.5.
GH: 5–19 dGH.
Ammonia / nitrite: 0 ppm sustained.
Nitrate:< 20 ppm.

Tank mates

Compatible with:

Other active community species (rosy barbs, white cloud minnows)
Corydoras catfish
Larger peaceful tetras
Loaches

Avoid:

Long-finned slow species (bettas, fancy goldfish, angelfish) — fin-nipping risk
Very small fish (chili rasboras, baby shrimp)

Frequently asked questions

How many zebra danio should I keep?: Minimum 6; for community-tank stability and proper behavior, the high end of the range is more reliable. Solo or paired individuals of schooling species typically hide and stop displaying normal behavior.
What tank size do I need?: Realistic minimum is 20 gal long. Smaller tanks technically house the species but compress the social and territorial dynamics in ways that show up as stress over time.
What water parameters does this species prefer?: Temperature 64–77°F (18–25°C), pH 6.5–7.5, GH 5–19 dGH. Tank-bred commercial stock typically tolerates a wider range than wild-type fish, but parameters in the middle of the listed range produce the most consistent behavior.

Stocking density calculator — verify community compatibility before adding zebra danio.
Tank volume calculator — confirm working volume vs nominal tank size.
Cycling a new aquarium — non-negotiable before adding any fish.
Water parameters explained — context for the temp / pH / GH ranges above.

Not veterinary advice — for sick fish or tank emergencies, consult an aquatic veterinarian or a qualified local aquarium professional.

Sources: FishBase species page. Mainstream hobby references (Aquarium Co-Op, Tetra, Hagen care sheets) used for hobbyist-context framing only — not cited as anchors for numerical claims. Where sources diverged, this guide takes the conservative beginner-safe position.

Zebra Danio care