Guppies: Bright, Busy and Very Good at Making More Guppies

Guppies and Endler's guppies are hardy, colorful livebearers. Keep at least three, two females to each male, or males only to avoid babies, in a heated, planted tank of at least about 12 gallons (45 liters) at about 68–82°F (20–28°C). They like harder water, a flake with algae in it, and no fin-nipping tank mates. Plan for fry: breeding is almost certain in mixed groups.

Figures from the Ornamental Aquatic Trade Association (OATA)'s guppy and molly care sheet; check your species' needs with a specialist keeper or aquatics store.

Guppies at a glance
Group	At least 3: two females to each male, or males only
Size	About 2 in (5 cm); Endlers about 1 in (2.5 cm)
Tank	At least about 12 gallons (45 liters)
Temperature	68–82°F (20–28°C)
pH	7.0–8.0, medium to hard water
Food	Flake with algae plus small frozen foods
Breeding	Almost certain in mixed groups

Colorful and Easy, With a Catch

Guppies come in an amazing range of colors and tail shapes, but OATA notes they are all one of two species: the traditional guppy (Poecilia reticulata), about 2 inches (5 cm), and the smaller Endler's guppy (Poecilia wingei), about 1 inch (2.5 cm). They are hardy, lively and easy to keep.

The catch is babies. Guppies are livebearers, and OATA describes breeding as almost a certainty.

Males, Females and Babies

Males are smaller and more colorful, with a rod-shaped anal fin called a gonopodium; females have a triangular anal fin. OATA suggests at least three together, two females to each male, so no female gets chased constantly.

OATA notes females may produce 20 to 80 fry after a pregnancy of 24 to 30 days. If you don't want a population boom, keep males only, which is a popular, colorful option. See livebearers for managing fry.

Tank and Water

OATA recommends at least about 12 gallons (45 liters) for a small group.

Temperature: about 68–82°F (20–28°C).
Water: guppies prefer harder, slightly alkaline water: pH about 7.0–8.0, medium to hard.
Gentle flow: long fins tire in strong currents.
Plants: live plants for cover and for fry to hide in; no sharp decor.

Setting Up for Guppies

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A planted tank with a heater and gentle filter suits guppies. Fine-leaved and floating plants give fry somewhere to hide.

Feeding Guppies

OATA suggests a good-quality flake or granule with a high algae content, plus small live or frozen foods such as daphnia. Endlers may need smaller foods such as cyclops. Feed what they eat in a few minutes once a day.

Tank Mates

Avoid fin-nippers such as many barbs, and anything big enough to eat Endlers. Good company includes corydoras, small peaceful tetras and rasboras, and otocinclus.

Keeping Them Healthy

Most problems in small fish start with water quality. Test ammonia, nitrite and nitrate weekly, change about a quarter of the water each week with conditioned tap water, and rinse filter media in old tank water, never under the tap. Quarantine new fish if you can, and add them a few at a time so the filter keeps up.

Watch your fish every day at feeding time. Changes in swimming, color, breathing or hiding are early signs that something is wrong, so test the water first.

For fish treatments or medicines: see your vet or a pet supply store with trained staff. An aquatics store with trained staff, or a vet who treats fish, can help you work out what's wrong before you add anything to the tank.

Frequently Asked Questions

What new keepers ask about guppies.

How can I tell male and female guppies apart?

Males are smaller and more colorful, with a rod-shaped anal fin. Females are larger with a triangular anal fin.

How do I stop guppies breeding?

Keep males only. In mixed groups, breeding is almost certain.

How many babies do guppies have?

OATA notes females may produce 20 to 80 fry after a 24-to-30-day pregnancy.

Do guppies need a heater?

Yes, in most homes. OATA suggests about 68–82°F (20–28°C).