What Size Tank Do Zebra Danios Need?
Adult standard length 2.0 inches. Active swimmers: a group of at least 8-10 needs a 36 × 12 inch base, about 21 US gallons.
Full breakdown: how many fish per gallon. Full breakdown: how many fish in a 20 gallon tank.
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The figures
| Figure | Value | Source |
|---|---|---|
| Adult standard length | 2.0 in | Seriously Fish |
| Minimum aquarium base | 36 × 12 in | Seriously Fish |
| Approximate volume | 21 US gallons | Seriously Fish |
| Group / social | Active; group of at least 8-10 | Seriously Fish |
| Filter rating | 325-405 liters per hour | Seriously Fish |
| Filter rating in gallons per hour | 85.87-107.00 gph | Calculated from the published liters per hour ÷ 3.785 (Seriously Fish; 1 US gallon = 3.785 liters) |
| Temperature | 64-77°F | Seriously Fish |
| Heater on the profile | 50 watts, assuming a room around 68°F | Seriously Fish |
| Aqueon band that contains about 21 gallons | 100 watts for 15-40 gallons | Aqueon |
| Aqueon 50 watt band | 5-20 gallons (21 is above 20) | Aqueon |
Full breakdown: what size filter for a 20 gallon tank.
How to size it
Length is the point of this minimum. Seriously Fish calls zebra danios active and asks for a group of at least 8-10, on a 36 × 12 inch base. That 36 inch run is longer than the 24 inch base used for neon tetras, platies, cherry barbs, and harlequin rasboras, even though the adult fish is only 2.0 inches. About 21 US gallons is the volume that goes with the longer base. It is not the 31 inch base used for bronze corys.
Four times about 21 gallons is 84 gallons per hour, and five times is 105. The converted rating, 85.87-107.00 gph, follows that four-to-five turnover. Flow is not marked gentle.
The heater is where the two sources part. The profile lists 64-77°F and 50 watts, assuming a room around 68°F. Aqueon gives 50 watts to tanks of 5-20 gallons. About 21 is above 20, so it misses that band. It falls in the 100 watt band, 15-40 gallons, and it is short of the 150 watt band, which starts at 30. Read both: the species page says 50 watts, and the volume chart says a 21-gallon aquarium is a 100 watt tank. This page does not average 50 and 100 into a new wattage.
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Accessory: a 50 watt heater, the wattage printed on the zebra danio profile. Aqueon's band for about 21 gallons is 100 watts, shown in the table above. Shop a 50 watt aquarium heater on Amazon
Related pages
- Stocking calculator
- What size tank mollies need (same 36 × 12 in base)
- What size tank a bronze cory needs
- What size heater a 29 gallon tank needs
FAQ
What size tank do zebra danios need?
Seriously Fish lists a minimum base of 36 × 12 inches, about 21 US gallons, for Danio rerio, and says to keep an active group of at least 8-10. Adult standard length is 2.0 inches.
What filter rating is listed for zebra danios?
Seriously Fish lists 325-405 liters per hour. Dividing by 3.785 gives 85.87-107.00 gallons per hour. Four times about 21 gallons is 84 gallons per hour, and five times is 105.
Why do the heater figures disagree for about 21 gallons?
Seriously Fish lists 64-77°F and a 50 watt heater, assuming a room around 68°F. Aqueon lists 50 watts for 5-20 gallons and 100 watts for 15-40 gallons. About 21 gallons is above 20, so it falls in the 100 watt band only.
Sources
- Seriously Fish, Danio rerio. https://www.seriouslyfish.com/species/danio-rerio/. Accessed Oct 2, 2026.
- Aqueon, Heater Wattage Guidelines. https://www.aqueon.com/-/media/project/oneweb/aqueon/files/us/educational/aq_heater_wattage_chart.pdf. Accessed Oct 2, 2026.