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Gill's molly

Poecilia gillii

FreshwaterBrackishFish

Gill's molly (Poecilia gillii)
Pcv84 · CC BY-SA 4.0

Care at a glance

Temperature
72–86°F
22–30°C
pH
7.0–8.5
Adult size
3.9 in
10 cm
Minimum tank
26 gal
100 L
Temperament
Peaceful
Social behavior
Social
Swim level
Middle
Difficulty
Easy
Breeding
Livebearer · Easy
Rarity
Very rare
Family
Poeciliidae
Origin
Costa Rica, Panama

Overview

Gill's molly is a sturdy, active livebearer for a roomy community tank. It is easy to keep.

Did you know

Gill's molly is so adaptable that wild populations live everywhere from clear inland streams to salty coastal lagoons. The same fish can move between fresh and brackish water without trouble.

Caring for the Gill's molly

Keep Gill's mollies in a group with more females than males, in 26 gal (100 L) or larger. They grow to a good size and stay active, so give them a roomy tank with plants, open water and steady flow. Good light grows algae for them to graze. They swim mostly in the middle of the tank.

Give them hard, alkaline water at 72 to 86°F (22 to 30°C) and a pH of 7.0 to 8.5. They readily accept a little marine salt, and a small amount does no harm. Like other mollies, they graze algae and aufwuchs all day. Base the diet on a vegetable-rich flake or pellet, and add occasional frozen foods.

Gill's mollies are peaceful and get along with other calm fish that like hard water. Males are slimmer and fertilize females internally with a gonopodium, the modified anal fin shared across the family.

Females carry the embryos and give birth to live fry. They breed easily in hard water and can produce large broods, so a group will steadily grow if the fry have cover.

Good to know

Gill's molly, Poecilia gillii, is a livebearer in the family Poeciliidae and one of the larger wild mollies.

In the wild

Poecilia gillii is widespread on the Atlantic and Pacific slopes of Costa Rica and Panama. It lives in warm lowland streams, ditches and coastal lagoons, so it is used to hard, mineral-rich conditions.

Weekly picks

Tank mates

The Gill's molly is a peaceful, social species that keeps to the middle. These picks share a community profile with it, are safe together in both directions, and overlap on water type, temperature and pH.

Check the full mix in the stocking calculator

Common questions

What size tank does a Gill's molly need?

A Gill's molly needs at least 26 gal (100 L). It spends most of its time in the middle.

What temperature and pH does a Gill's molly need?

A Gill's molly is comfortable at 72–86°F (22–30°C) with a pH of 7.0–8.5.

What does a Gill's molly eat?

A Gill's molly grazes algae and aufwuchs all day. Base its diet on a vegetable-rich flake or pellet, and add occasional frozen foods.

How big does a Gill's molly get?

An adult Gill's molly reaches about 3.9 in (10 cm).

How can you tell a male Gill's molly from a female?

Males are slimmer than females and carry a gonopodium, the modified anal fin of the family.

How does a Gill's molly breed?

Gill's mollies are livebearers, and the females give birth to live fry. They breed easily in hard water and can produce large broods.

Related species