TankBud

Giant sailfin molly

Poecilia velifera

Also known as Yucatan molly

FreshwaterBrackishFish

Giant sailfin molly (Poecilia velifera)
Matteo Cassella · CC BY-SA 4.0

Care at a glance

Temperature
75–82°F
24–28°C
pH
7.5–8.5
Adult size
5.9 in
15 cm
Minimum tank
30 gal
113 L
Temperament
Mostly peaceful
Social behavior
Social
Swim level
Middle
Difficulty
Medium
Breeding
Easy
Rarity
Common
Family
Poeciliidae
Origin
Yucatan Peninsula, southeastern Mexico (Yucatan, Quintana Roo, Laguna de Terminos systems)

Overview

Keep them in a group with more females than males, around two or three females per male, since lone males pester females without a break. Give them at least 113 liters, more if you can, and keep the water warm at 24 to 28 C, hard, and alkaline at pH 7.5 to 8.5. Soft, acidic water makes them shimmy, clamp their fins, and sicken, so skip the blackwater community look. They sit in the middle of the tank and are mostly peaceful, though their size and constant mating drive make them a poor match for timid nano fish. Feed an algae heavy diet with vegetable matter alongside regular foods. They breed on their own with no effort, so give the fry plants or cover or the adults will eat them. Never release unwanted fish into local waters, and check your local rules first.

In the wild

Giant sailfin mollies come from the coastal lowlands of the Yucatan Peninsula in southeastern Mexico, across the Yucatan, Quintana Roo, and Laguna de Terminos systems. These are hard, alkaline waters, often with some salt mixed in near the coast. Match that with a roomy tank of at least 113 liters, a long footprint of about 90 cm, and water on the hard, alkaline side at pH 7.5 to 8.5. Plant it well and leave open swimming room down the middle. Many keepers add a little marine salt, which this fish tolerates and often appreciates.

Good to know

This is Poecilia velifera, a livebearer in the family Poeciliidae and the largest of the common mollies. Females reach around 15 to 17.5 cm and males about 15 cm, so it gets big. Males grow a tall, fan shaped sailfin dorsal that only develops properly in a spacious, uncrowded tank. Like other mollies it bears live young rather than laying eggs.

Did you know

The sailfin that gives this fish its name is mostly for show. Males raise and flare that big dorsal at females and at rival males in a slow display, and the fin only reaches full size in a tank with enough room to grow. Crowd them as youngsters and the males stay stunted with a smaller fin for life.

Weekly picks

Tank mates

Giant sailfin molly is a mostly 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 Giant sailfin molly need?

A Giant sailfin molly needs at least 30 gal (113 L). It spends most of its time in the middle.

What temperature and pH does a Giant sailfin molly need?

A Giant sailfin molly is comfortable at 75–82°F (24–28°C) with a pH of 7.5–8.5.

How big does a Giant sailfin molly get?

An adult Giant sailfin molly reaches about 5.9 in (15 cm).

Related species