Mollies – Peaceful and Unpretentious

Mollies are a small group of viviparous fish from the Peciliaceae family. The name is historical, due to the fact that earlier they were attributed to the genus Mollienesia. According to the modern classification, they belong to the genus Poecilia.


General information

Very popular and unpretentious fish in care, the maintenance of which will not cause problems even for inexperienced aquarists. Thanks to the selection, a large number of forms were obtained, differing in color and body shape.

For mollies, like other Liliaceae, egg production is characteristic. This means that fertilization and development of eggs occur in the womb of the female, and a relatively large, formed fry is born, ready for independent feeding. This only adds popularity to the fish, because getting offspring from it is easier than ever, even in a general aquarium.

The fish are peaceful, rather large, and mobile, therefore they will decorate any aquarium with non-aggressive species.


Mollies are very beautiful fish. The natural color of the fish is yellowish-gray or silvery, gray-bluish, bluish-black, or yellow-green spots are scattered over the entire surface. The body is elongated and laterally compressed, the head is medium-sized, the mouth is upper, the eyes are rather large. The fins of most species are short, with the exception of the velifer mollies, which have a very developed dorsal fin. The caudal fin is rounded. Females in all mollies are larger than males and can reach up to 10 cm in size. Sexual dimorphism is pronounced: males are smaller than females and have a special reproductive organ – gonopodia. It is a modified anal fin, in the form of a tube, thanks to which the male can introduce reproductive products into the female’s body. The anal fin in the female is triangular, rounded.

Thanks to the efforts of breeders, a wide variety of mollies with various colors have been obtained: black, yellow, snow-white, and others. Forms with a lyre-shaped tail fin and balloons (have a shortened body and a convex abdomen) are very popular.

History of appearance/discovery

The first of the described types of mollies was the Sphenops Polynesia. The description was given by the French zoologist Achille Valenciennes in 1846 in the course of work on the 22-volume work “Natural History of Fish”.

More than 50 years later, the famous ichthyologist-taxonomist Charles Tate Regan, following the results of studying samples in the British Museum of Natural History, described free mollies and velifer mollies.

In 1913, the mollies latipina came to Europe.

Since 1920, active selection work began, various hybrids began to appear one after another. This, first of all, was facilitated by the possibility of crossing between the three main types of mollies: Sphenops, latipina, and vinifera.

Fish are rapidly gaining popularity among aquarists. In 1925, a black-speckled form was obtained by careful selection of Sphenops mollies on fish farms in Florida. We owe this to the American breeder Jack Bitter. Further selection was continued by a German by origin – Bill Sternke, who immigrated to the USA in 1908. It took him 11 years to get an absolutely black velvet shape of mollies. The breed was named Black Molly. She is the most demanded breed to this day. When the word “mollies” is used, most aquarists remember the black molly, this is the most recognizable breed. This fish came to our country after 10 years, the peak of its popularity falls in the 60s. Later, Sternke received albino mollies, called gold.

The latest trend was the appearance of mollies with a shortened body and a convex abdomen – balloons.


The natural habitat of mollies in the southeastern part of the United States, Central America, and the north and east of South America. You can find these fish both in freshwater bodies and in the mouths of rivers flowing into the ocean. In these places, there is a mixture of fresh water from rivers and saltwater from the ocean. But even despite this, some populations of mollies easily adapted to the increased salinity.

Mollies Sphenops is widespread in waters from Mexico to Colombia. High fin view – vinifera
– is endemic to the Yucatan Peninsula (Mexico). Molliesia latipina prefers reservoirs of the southern states of the United States (Texas, Florida, Carolina, Virginia), gravitates to brackish water.

Unpretentiousness, omnivorousness, and ovoviviparity allowed mollies to populate vast tropical regions of Central and South America.

As for aquarium forms, they are massively bred on special fish farms, including in the countries of Southeast Asia, from where they are sold to other countries. Fish can be found in aquariums of amateurs all over the world.

Care and maintenance

Mollies are one of the most unpretentious fish. It is best to keep them in small flocks of 7-10 individuals. In order to reduce intraspecific aggression, it is best to select the fish so that there are two or three females per male. The minimum aquarium volume recommended for mollies is 50 liters. For a velifer, it is better to choose a volume of 100 liters or more, since they are much larger than their counterparts. Fish love to swim actively, so it is recommended to purchase a classic rectangular aquarium with a lid: mollies often jump out of the water. Fish love bright lighting, the length of daylight hours should be at least 12 hours.

The design of the aquarium can be chosen according to your taste. It is better to use pebbles of the middle fraction of dark color as soil. Several snags or rocks can be installed. Females can hide there if they are not ready to spawn. Fish swim mainly in the upper and middle layers of the aquarium.

Mollies are very hardy fish and are able to adapt to a wide range of water parameters. However, it is still recommended to create the most optimal conditions in the aquarium. Mollies love warm water with a temperature of 23-28 ° C. You should not allow sudden temperature fluctuations, this is very bad for the health of the fish. For their content, neutral or slightly acidic water is suitable (pH = 7-8). But mollies do not like too soft water, it is better than the hardness is from 10 to 20 ° dGH.

Many mollies are able to live in slightly brackish water. Very often in the literature, it is recommended to periodically add some salt to the water in aquariums with mollies (up to a concentration of 2-3 g / l). It is best to use special sea salt for this purpose. But it is worth recalling that this is only possible with a separate keeping of fish. In the case of a shared aquarium, this may be unsafe, as the neighboring fish may not tolerate increased salinity. There must be sufficient filtration and aeration in the aquarium. Do not forget about regular water changes: weekly you need to replace 25-30% of the aquarium water with fresh water.

Mollies thrive in aquariums with live plants. It will be helpful to create dense patches of vegetation, remembering to leave some space for swimming. Mollies love to eat up the delicate leaves of some plants. They are also able to scrape off algae from the surface of the scenery and the ground.

Mollies are a good indicator of aquarium health. In the case of a lack of oxygen, they are one of the first to rise to the surface of the water, and in the case of the accumulation of metabolic products, they slow down and fold their fins, or move in jerks.

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