Betta tank size
Five gallons is the usual minimum. A 15 gallon tank meets every guide we use.
Care guides give different answers because one names a volume and the other a floor space. A tank that satisfies both is a 15 gallon or larger.
What the care guides say
- Aquarium Co-Op: a minimum of 5 to 10 gallons, with a heater and a gentle filter.
- Seriously Fish: a base of 45 x 30 cm, about 18 x 12 inches, for a single male or a pair. Water at 72 to 86°F.
An adult betta is about 70 mm (under 3 inches) long, so the tank size is about swimming room and stable water, not the fish’s length.
Which tanks meet each guide
The Seriously Fish footprint is about 18 x 12 inches. A tank within 5% of that counts.
| Tank | Length x width | Seriously Fish footprint | Co-Op 5+ gallons |
|---|---|---|---|
| 2.5 Gallon | 12 x 6 in | Under | Under |
| 5 Gallon | 16 x 8 in | Under | Yes |
| 10 Gallon | 20 x 10 in | Under | Yes |
| 15 Gallon | 24 x 12 in | Yes | Yes |
| 20 Gallon Long | 30 x 12 in | Yes | Yes |
| 29 Gallon | 30 x 12 in | Yes | Yes |
A 10 gallon tank meets the volume advice but is about two inches narrower than the footprint Seriously Fish recommends.
One betta per tank
Keep one betta per tank. Seriously Fish lists the betta as a solitary, long-finned anabantoid, and notes that males see long-finned or similar-shaped fish as rivals, so it is not suited to a standard community. If you want company for one, the stocking calculator has a 20 gallon long with a betta and 8 harlequin rasboras that passes its checks.
Sources: Seriously Fish, Aquarium Co-Op.
Common questions
What size tank does a betta need?
Aquarium Co-Op recommends 5 to 10 gallons as a minimum. Seriously Fish gives a base of 45 x 30 cm, about 18 x 12 inches. A 15 gallon tank meets both.
Can a betta live in a 5 gallon tank?
Yes by the Co-Op volume guide, with a heater and a gentle filter. It is smaller than the footprint Seriously Fish recommends, so a 10 or 15 gallon gives the fish more room.
Can two bettas live together?
Keep one betta per tank. Males fight, and they also see long-finned or similar-shaped fish as rivals.
What temperature does a betta need?
72 to 86°F, so a heater is needed in most rooms.
Gear for a betta tank
Searches on Amazon for the right size. Check the tank size or flow rating on the listing before you buy.
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