What Size Tank Do Guppies Need?

Adult standard length 2.4 inches. The published tank is 18 × 12 × 12 inches, about 11 US gallons.

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

Quick answer: Guppies (Poecilia reticulata) need a tank of 18 × 12 × 12 inches, about 11 US gallons, at an adult standard length of 2.4 inches (Seriously Fish). The profile does not add a group count, and it lists a filter of 165-205 liters per hour (43.59-54.16 gallons per hour), 63-82°F, and a 50 watt heater. Aqueon also lists 50 watts for 5-20 gallons, and about 11 gallons falls in that band rather than the 100 watt band that starts at 15.

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The figures

Figure	Value	Source
Adult standard length	2.4 in	Seriously Fish
Minimum aquarium	18 × 12 × 12 in	Seriously Fish
Approximate volume	11 US gallons	Seriously Fish
Group / social	No group count is given on the profile figures used here	Seriously Fish
Filter rating	165-205 liters per hour	Seriously Fish
Filter rating in gallons per hour	43.59-54.16 gph	Calculated from the published liters per hour ÷ 3.785 (Seriously Fish; 1 US gallon = 3.785 liters)
Temperature	63-82°F	Seriously Fish
Heater on the profile	50 watts, assuming a room around 68°F	Seriously Fish
Aqueon band that contains about 11 gallons	50 watts for 5-20 gallons	Aqueon

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

How to size it

The footprint matches the betta minimum (18 × 12 inches, about 11 US gallons), and the guppy profile adds the height: 18 × 12 × 12 inches. Adult standard length is 2.4 inches, a bit under the betta's 2.8 inches. Seriously Fish does not print a schooling minimum, so this page does not borrow one from another species.

165 ÷ 3.785 = 43.59 gph. 205 ÷ 3.785 = 54.16 gph.

Four times about 11 gallons is 44 gallons per hour, and five times is 55. The converted rating, 43.59-54.16 gph, sits on that four-to-five band. The profile does not mark the flow as gentle, so there is no reason on these figures to drop to the betta's 21.14-33.03 gph sponge range.

Temperature is the wide one in this set: 63-82°F, with a 50 watt heater assuming a room around 68°F. Aqueon agrees on 50 watts, because 5-20 gallons contains about 11. The 100 watt band starts at 15 gallons and does not contain 11. A 50 watt heater is the watt both sources name for this volume.

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Accessory: the 50 watt heater named on the guppy profile and on Aqueon's 5-20 gallon line. Shop a 50 watt aquarium heater on Amazon

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