Hardy, easy to breed and relatively adaptable, Mollies can live in both freshwater and saltwater if acclimated slowly. They are very active swimmers and their aquariums should be heavily planted leaving an abundance of open swimming space.
Quick stats – Mollies
|Max size||3” / 7 cm|
|Aquarium||Min 25 gallon / 90 liters|
|Water||70-82° F / 21-28° C|
KH 10-25, pH 7.0-8.0
|Colors||Black, yellow, red, orange|
Mollies are freshwater fish belonging to the Poeciliidae family. Even though they now belong to the Poecilia genus, they still bear the name ‘Mollies’ because they used to belong to the Mollienesia genus.
Originally, they are only found particularly in the river basins, lakes and ponds of North and South America, but recently they have been introduced to other countries including parts of Eastern Europe, Singapore, Taiwan, Colombia, Japan and Israel.
They are elongated and laterally compressed. They exhibit sexual dimorphism with the female being larger than the male in all species.
As the males mature, they develop a gonopodium which is a narrow copulatory organs with a strong hook which results from the modification of the middle rays possessed by the anal fin.
There are different varieties of Mollies, but having two basic distinctions; with some having a small dorsal fin while others possess a large dorsal fin.
There are three main common variety of the Mollies which includes, The common or Short-finned Molly (Poecilia sphenops), Sailfin Molly (Poecilia latipinna), and the Mexican Sailfin Molly (Poecilia velifera) each having their various distinguishing features.
The common or Short finned Molly (Poecilia sphenops)
As the name implies, these are the most common type of Molly, possessing a short fin. They are the smallest species of the three varieties possessing a rounded and compact fin. Their dorsal fin starts behind the anal fin and has about 14 rays on the dorsal fin.
Just as with every other Molly, the male is smaller than the female, with the male having a slim and elongated body than the females which are rather plump.
In the wild, they can grow to an exceeding size of 8’’ (20cm). However, in the tank, their growth is restricted with the male growing to about 3’’ (8cm) while the female grows to 4-5’’ (10-12cm). However, the males are more radiantly colored than the females.
They have several subspecies that have been selectively bred which come in varying colors, but mainly occurring in blue coloration usually with a yellow or red fin.
The popular Black Molly is a selective breed of the short-finned molly. It usually has an olive brown back and a silvery side having a blue or green luster distinctly marked with several brown or orange dots.
Although they are originally Short-finned species, recently they have been selectively crossbred to produce larger fins species such as the popular Lyretail Molly. But these hybrid species are not hardy, require warmer water and are prone to diseases.
The Sailfin Molly (Poecilia latipinna)
Otherwise called the Topsail Molly, these species are one of the most attractive species of the Mollies. They belong to the group of Mollies that possess a large dorsal fin.
However, they have a similar shape with the Common Mollies but are more rectangular in shape and are more laterally shaped. Their fins are beautified with dark rectangular spots. They have their dorsal fins right in front the anal fin.
In the wild, they can grow to an exceeding size of 8’’ (20cm) but just like the common molly, their growth is restricted in the aquarium, only growing to about 4-5’’ (6-12cm).
They also have several subspecies that have been selectively bred which come in different colors, usually, melanistic, leucistic, albino, and prominently green with black dots.
The Midnight Molly is a selective breed of the Sailfin Molly possessing an all black coloration.
Mexican Sailfin Molly (Poecilia velifera)
Also known as the Giant Sailfin Molly or the Yucatan Molly, the male Mexican Sailfin Molly has a striking resemblance and it’s rather hard to distinguish from the Sailfin Molly, also having their dorsal fins right in front the anal fin.
However, the Mexican Sailfin Molly has a slightly different fin where they possess small round light spots on the dorsal fins and have about 18 rays on their dorsal fin.
They occur in a natural green body often with dark spots and can also have an albino strain.
In the wild they can grow up to 8’’ (20cm), but just like every other Molly, their growth is restricted in the aquarium where they can only grow up to 6’’ (15cm).
Mollies in the natural habitat
The Mollies are often regarded as American fish because they are originally found only in rivers, lakes and ponds of North and South America. But in recent time, they have been introduced to other countries, including parts of Europe and Asia.
They are often found in moderate moving water, slightly alkaline and having a hardness of 20-30 dGH. However, the pH range and temperature might slightly differ from the three main species.
As omnivores, they feed on meaty foods and vegetables. However, they have a large craving appetite for vegetables.
Mollies in the ideal aquarium
Setting up the ideal aquarium for Mollies will require a well filtered 20 gallon to house a Molly male with a few companions. The water flow should be moderate with a hardness of 20-30 dGH and depending on the type of Molly you wish to house, the temperature and pH value may vary.
The Common and Sailfin Molly will do well in a tank with 21.1-27.8˚C (70.0-82.0F), while the Mexican Salfin Molly would thrive better in a bit warmer tank having a temperature of 22-28˚C (72-82F). The suitable pH level for the Common and Sailfin Molly would range within 7.0-8.5, while the Mexican sailfin Molly would require a pH level of 7.5-8.2.
To maintain a high hygiene and a safe tank, the water should be changed every 2 weeks replacing up to 30% of the water at each interval. This will also help to improve the coloration of the male species. Moreover some molly species have a low tolerance for poor water conditions.
They do not prefer a particular substrate as these species are active swimmers and are usually seen in the middle and upper region of the tank. However, light gravels will do just fine for the tank’s substrate.
All mollies thrive in a well-planted tank, though should not be overcrowded because they are active swimmers and need a lot of swimming space. These plants may serve as shades and should also supplement nutrition in the tank.
Because they have a strong appetite for vegetables, the plant decorations should be carefully selected. Too much driftwood should be avoided, as driftwood reduces the pH level of water and these species don’t thrive in an acidic medium.
They do not prefer strong lighting, so a moderate normal lighting would just be perfect for the tank.
Though they are active swimmers, they are generally peaceful and social too, but are most comfortable in the company of their own same species. However, some Mollies have been observed to be rather aggressive and can squabble with other species but without causing any harm.
Suitable tankmates for Mollies should be of the same temperaments and adaptive to their water conditions too. Suitable companions include Corydoras, Rainbowfish, Barbs, Characins, Tetras, Cyprinids and members of the Poecilia family. Also invertebrates such as Shrimps and Snails are safe with the Mollies.
Mollies can have a long fin, so they should not be housed with fellow fin-nippers such as the Tiger barb. Aggressive and large semi-aggressive species are unsuitable tankmates for the Mollies as they will harm the peaceful Mollies and make them uncomfortable.
As omnivores, Mollies can feed on meaty foods and vegetables. However, they tend to have a strong appetite for vegetables; this requires that most of their diet should contain lots of vegetables and algae too.
As a matter of fact, the development of the male Sailfin Molly’s dorsal fin will be greatly affected and impaired if they are not adequately fed with enough vegetables. Cucumber or blanched spinach will serve their vegetarian appetite.
Also meaty food (live and frozen) would make a yummy treat for the Mollies. Brine shrimp, tubifex, or bloodworm would make the day for Mollies.
Their meal can be supplemented with high quality protein and vitamin rich flakes and pellets. They should be fed several times a day with just a small quantity of food they can finish in a few minutes of 2-3. Every leftover should be immediately removed.
Breeding Mollies is quite easy and straightforward, but the Mexican Sailfin Mollies could be a bit more difficult. They are livebearers and will readily breed in their aquarium.
However, to encourage breeding, a breeding tank of about 20 gallons can be prepared and a breeding pair introduced. A male with 2-3 females can be kept. The water temperature should be around 26˚C (79F).
The gestation period is 28 days, after which the female Common molly will produce about 20-150 fry, the female Sailfin Molly will produce about 10-100 fry while the female Mexican Sailfin Molly will commonly produce 20-60 fry, but can produce as much as 200 fry.
Their fry can be fed with smaller live food like baby brine shrimp and crushed vegetables until they are mature to feed on heavier foods.
Mollies are hardy fish belonging to the Poeciliidiae family. They are peaceful and social too.
Depending on their patterning and body shapes, they are mainly divided into three categories including the Common (short-finned) Molly, the Sailfin Molly, and the Mexican Sailfin Molly. However, many subspecies of these varieties have been selectively bred.
They are often regarded as brackish species, but can do well in freshwater provided the water is not soft and/or acidic. They are omnivores, but have a high appetite for vegetables.
Breeding is quite easy for the mollies, and they give birth to live fry. With proper care and the right tank conditions, Mollies can live up to 5 years.
Are Mollies egg laying fish?
No, Mollies are livebearers, producing dozens of live fry.
What is the maximum size of Mollies?
In the wild Mollies can grow up to 8″ (20cm), but their growth is constrained in the tank, growing within 4-6″ (10-15 cm).
How long can Mollies live?
With proper care and the right tank conditions, Mollies can live up to 5 years.
What are suitable tank mates for Mollies?
Suitable tankmates for Mollies include Corydoras, Rainbowfish, Barbs, Characins, Tetras, Cyprinids and members of the Poecilia family. Also invertebrates such as Shrimps, Crabs and Snails are compatible. However, they are most suitable with more Mollies.
What are the food requirements of Mollies?
They are omnivores, but have a strong herbivorous appetite. Most of their meals should contain enriched vegetables such as Cucumber and Spinach. They also enjoy meaty foods such as tubifex, bloodworm or brine shrimp. Their meal can be supplemented with high quality flaked enriched with vitamins and protein.