Guppy Identification Guide
How to identify a guppy and tell males from females.
Read the full Guppy encyclopedia entry →The Guppy (Poecilia reticulata) is a tiny, hardy livebearer and one of the most popular aquarium fish in the world.
Key identification features
- Very small size, males about 3 cm and females about 6 cm.
- Colorful, patterned tails and bodies in males — spots, stripes, and bright hues.
- A rounded body with an upturned mouth for surface feeding.
- Livebearing: females give birth to free-swimming young rather than laying eggs.
Male vs. female
- Males: smaller, slimmer, vividly colored with large ornate tails, and a rod-like anal fin (gonopodium).
- Females: larger, plainer grey-silver, with a fan-shaped anal fin and often a dark 'gravid spot' near the belly.
Similar livebearers
- Endler's Livebearer: closely related and very similar, but smaller and with more metallic, blocky color patterns.
Where you'll see one
Guppies are aquarium fish native to northern South America and widely naturalized. A tiny, colorful livebearer with an ornate tail is almost certainly a male guppy.
Frequently asked questions
How do I tell a male guppy from a female?
Males are smaller, brightly colored with large fancy tails and a rod-shaped anal fin, while females are larger, plainer, and often show a dark gravid spot.
Do guppies lay eggs?
No, guppies are livebearers — females give birth to free-swimming young.