AquariumStocking

What Size Tank Does a Betta Fish Need?

Adult standard length 2.8 inches. The published minimum is an 18 × 12 inch base, about 11 US gallons.

Full breakdown: how many fish per gallon. Full breakdown: how many fish in a 20 gallon tank.

Quick answer: A betta (Betta splendens) needs a minimum base of 18 × 12 inches, about 11 US gallons, which Seriously Fish calls large enough for a single male or a pair. The same profile says the fish is best kept alone and does not support tiny tanks or jars. Hold 72-86°F with a 50-100 watt heater on gentle flow of 80-125 liters per hour (21.14-33.03 gallons per hour); Aqueon places about 11 gallons on the 50 watt band for 5-20 gallons, not on the 100 watt band that starts at 15 gallons.

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The figures

FigureValueSource
Adult standard length2.8 inSeriously Fish
Minimum aquarium base18 × 12 inSeriously Fish
Approximate volume11 US gallonsSeriously Fish
Group / socialLarge enough for a single male or a pair; best kept alone; tiny tanks and jars are not supportedSeriously Fish
Filter rating80-125 liters per hour, gentle flowSeriously Fish
Filter rating in gallons per hour21.14-33.03 gphCalculated from the published liters per hour ÷ 3.785 (Seriously Fish; 1 US gallon = 3.785 liters)
Temperature72-86°FSeriously Fish
Heater on the profile50-100 watts, assuming a room around 68°FSeriously Fish
Aqueon band that contains about 11 gallons50 watts for 5-20 gallonsAqueon
Aqueon 100 watt band15-40 gallons (starts above 11)Aqueon

Full breakdown: what size filter for a 20 gallon tank.

How to size it

Seriously Fish publishes the filter in liters per hour. The conversion used here is 1 US gallon = 3.785 liters, so gallons per hour = liters per hour ÷ 3.785.

80 ÷ 3.785 = 21.14 gph. 125 ÷ 3.785 = 33.03 gph. Shop the gentle-flow range, not a stronger current.

The same source sizes ordinary filters at four to five times the tank volume per hour, and it sets that rule aside when the species wants gentle flow. Four times about 11 gallons is 44 gallons per hour, and five times is 55. The published gentle rating converts to 21.14-33.03 gph, which sits below that four-to-five band. Use 21.14-33.03 gph, and choose a sponge filter so the outlet is not a jet.

On heat, the profile lists 72-86°F and 50-100 watts, with the heater figure assuming a room around 68°F. Aqueon lists 50 watts for 5-20 gallons. About 11 is inside 5-20, so the 50 watt line includes this minimum. The 100 watt line is 15-40 gallons, and 11 is below 15, so that line does not include it. The profile's 50-100 watt span is wider than the single Aqueon band that contains 11 gallons; both figures are reported above, and neither chart is rewritten here.

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Accessory: a heater at the 50 watt end of the profile's 50-100 watt span, which is also the Aqueon band for this volume. Shop a 50 watt aquarium heater on Amazon

Related pages

FAQ

What size tank does a betta fish need?

Seriously Fish lists a minimum base of 18 × 12 inches, about 11 US gallons, for Betta splendens. That base is described as large enough for a single male or a pair, and the profile does not support tiny tanks or jars.

What filter flow does a betta need?

Seriously Fish rates the filter at 80-125 liters per hour and marks the flow as gentle. Dividing by 3.785 converts that rating to 21.14-33.03 gallons per hour, which is below four to five times an 11-gallon volume (44-55 gallons per hour).

What heater wattage matches an 11-gallon betta tank?

Seriously Fish lists 72-86°F and a 50-100 watt heater, assuming a room around 68°F. Aqueon's 50 watt band is 5-20 gallons, which includes about 11 gallons. The 100 watt band starts at 15 gallons, which does not.

How many bettas does this minimum hold?

Seriously Fish calls the 18 × 12 inch base large enough for a single male or a pair, and says the fish is best kept alone.

Sources