Max Size: 12cm

Mollies (Poecilia Sphenops)

Mollies are colourful live-bearing freshwater fish. There are currently 39 known species in this genus. Mollies are one of the most commonly kept fish amongst hobbyists and are perfect for beginner aquarists as they are very hardy and easy to take care of.

Mollies are active and sociable and enjoy schooling together. However, a shoal should be predominantly female because males are known for harassing and stressing out females, and you should have at least four or more individuals.

You will see plenty of unique personalities and exciting behaviours begin to develop. For example, Mollies are peaceful fish most of the time but can show signs of aggression when surrounded by aggressive tank mates or are overcrowded. Therefore, it’s essential that their tank is big enough and that they have suitable tank mates.

Suitable tankmates can include Corydoras Catfish, Danios, Dwarf Gouramis, Cherry Barbs, Rasboras, Rosy Barbs, Platies, Tetras and Loaches. Most invertebrates such as Shrimp and Snails will be fine living alongside your Mollies also as they will mostly ignore them. However, it is recommended that you avoid larger, more aggressive fish such as Cichlids as these will try to eat your Mollies and may attack and stress them out to the point of death.

There are plenty of different varieties of Mollies, although most are very similar to the common Molly. The main differences are patterns and colours, but shapes and sizes can differ too.

The common Molly has a flattened body, is tall in the middle and narrows towards a point at the mouth. Their caudal fin is a large fan shape that can be colourful or transparent, and their dorsal fin can be elevated as a fan, resembling the caudal fin or flattened against the body.

You also have the Black Molly Fish that is black all over, as well as the Sailfin Molly. The Sailfin Molly variety is bred in several colours and patterns, and their most distinctive feature is their large dorsal fin which is much taller and runs from behind the head to the caudal fin.

Lyretail Mollies stand out because of their caudal fin; the top and bottom of the fin narrow into a point that trails behind the rest of the fish. Other popular Mollies include the Balloon Molly, Dalmatian, Molly, Red Molly, the Orange Molly and the White Molly.

Quick Facts
Scientific NamePoecilia Sphenops
Other NamesShort-finned Molly, Sailfin Molly, Common Molly, Black Molly, White Molly, Golden Molly, Lyretail Molly, Dalmatian Molly
OriginsColombia, Mexico, Venezuela
Aquarium LevelAll Levels
DifficultyBeginner - Intermediate
Best kept asGroups 5+
Lifespanup to 5 years
Water Parameters
Water TypeFreshwater
PH6.5 - 8.5
GH15 - 30
72 - 78℉
22.2 - 25.6℃


Lyretail Molly
Dalmatian Molly
Lyretail Molly
Balloon Molly
Sailfin Molly
Dalmatian Molly

Natural Habitat

Mollies natural range moves north from Colombia and Venezuela to Mexico, with separated populations on some Caribbean islands. Wild fish are scarce in the hobby these days, though, with the vast majority of the mass-produced sales in Eastern Europe and the Far East. Nevertheless, feral or introduced populations also exist in a handful of other countries, including the United States, Japan, Singapore, and even Eastern Europe.

Mollies typically inhabit shallow parts of rivers and streams with sandy substrate covered in debris and rocks usually surrounded by aquatic plants. However, you can also found these fish in a wide variety of different habitats, including coastal sea waters and brackish swamps.


Mollies are omnivores, feeding on a variety of detritus and zoobenthos in the wild. In the aquarium, these fish will accept most foods offered, including good quality flake food as well as live and frozen food. However, a significant proportion of their diet should be made up of vegetable matter such as blanched spinach, zucchini or vegetable flake.

Sexual Dimorphism

It is relatively straight forward to distinguish male from female Mollies. Males are smaller, brighter coloured and possess a pointed anal fin called the gonopodium. In contrast, females are larger than males, have rounder stomachs, and their anal fin is fan-shaped rather than pointy.


Breeding Mollies is very easy if you provide the right water conditions. These fish reproduce in a standard livebearer style. Like other species, males can be somewhat constant in their pursuit of females, so it is recommended that you keep several females to every male to diffuse this.

Your tank will need to have plenty of areas of dense planting, as this will allow your mollies to feel secure and able to give birth and provide cover for the fry so that the survival rate may be higher.

The gestation period is usually around eight weeks, and large broods of up to 120 fry are not surprising. However, the adult fish will predate on the young, so the best method of raising them is to remove the pregnant females to a separate breeding tank allowing them to give birth there before returning them to the main aquarium. The use of breeding traps or nets is not advised because their small size is not suitable for raising the fry.

The fry is pretty large when they are born and will accept powdered flake food or baby brine straight away.

Other Livebearers of interest

Cardinal Brachyrhaphis(Brachyrhaphis roseni)
Dusky Millions Fish(Phalloceros caudimaculatus)
Humpbacked Limia(Limia nigrofasciata)
Merry Widow Livebearer(Phallichthys amates)
Platies(Xiphophorus maculatus, Xiphophorus variatus)
Spotted Skiffia Multipunctata(Skiffia Multipunctata)
View all Livebearers
Date Added: 07/05/2021 09:31:08 - Updated: 19/01/2022 14:54:50