• Scientific name: Poecilia latipinna
  • Common names: Molly fish
  • Family: Poeciliidae
  • Origin: North Carolina to Texas and the Yucatán Peninsula of Mexico
  • Temperament: peaceful
  • Maximum length: 3.2 inches (male) and 4.8 inches (female)
  • Lifespan: 3-5 years
  • Tank size: 20 gallon aquarium
  • Optimal pH: 7-8
  • Hardness: 10-25 dGH
  • Temperature: 78-82°F (25-27°C)
  • Lighting: medium
  • Filtration: medium
  • Aeration: medium.

Molly fish are very interesting and easy-to-keep fish for beginners. They are livebearers and give birth during their lifetime. The baby Mollies are very cute that makes this species a favorite of beginners.

About Molly fish

black-molly fish

The scientific name of Molly fish is Poecilia Latipinna and they are usually found in Mexico, Texas and Florida, California and Virginia areas. They have a relationship very close to Guppies, both species are of the Poecilia genus. Molly is also commonly seen in home aquariums as well. And it does not need a fish expert so you can breed it easily. This type of fish can simply breed while it is in your aquarium.

Molly fish come in varieties of colors which derive from only 3 primitive colors: white, orange, and black.

silver-sailfin-mollySilver Sailfin mollies, which actually look white

golden-mollyGolden Sailfin mollies, which are yellow-orange

black-molliesBlack Sailfin Mollies, which are full black

dalmatian-mollyDalmatian Sailfin Mollies with white body and black spots

Many other color variations available in the market are:

  • The Marble with its orange, black and yellow spots
  • The Red, which is orange but often has pink eyes
  • The Platinum, which is silver.  It is said that it will glow under a black light
  • The Green, which has a green hue.

The Mollies in previous images are Sailfin Mollies with long body lengths, there is also a form with shorter body called Balloon Mollies. Tail styles are also diverse with round tail and lyre tail (or moon tail).

balloon-molliesSo cute Balloon Mollies

The Molly is easy to interbreed between different colors that results in offspring with so many color combinations. It is best to keep only different variations in separate aquariums to avoid interbreeding and unwanted colored offspring.

Tank setup

molly-aquarium

Because this is a large fish, it should be kept in a large aquarium or a small pond with surface area being more important than depth. The tank should have many plants and decorations, plants help to increase the water aeration and provide hiding place for the fish. In addition, the plants also provide a little vegetable food source for Mollies.

At least a 10-gal tank for 2-3 for Balloon Mollies and a 20-gallon tank for 4-5 Sailfin Mollies are recommended to keep the fish happy and healthy. It is best that you have more than two females for every one male in each tank because males constantly chase females that may cause stress for them, especially when they are close to giving birth. Male Mollies are also known to aggressive towards each other as well.

Mollies are sensitive to increased nitrogenous wastes and low water temperatures. They prefer a little salt with their water, they can live in fresh or brackish water environments. Molly fish can be found normally where fresh water meets salt water in various regions of the world. By adding ½ teaspoon of marine aquarium salt to every gallon of water, you will make your Molly fish very happy.

Ensure that you properly add new purchased Mollies to your tank to avoid fish loss. Feed your existing fish before adding the new fish to make sure they don’t think the new mollies are food. Lay the bag of new coming fish in the tank for at least 10-15 minutes for the temperature equilibrium. Using a fish net to transfer the fish to your tank without introduction of the water from the bag.

Temperament and tankmates

Molly-in-community-aquariumA black Molly, Guppies and Plecos are sharing an algae wafer

Mollies are peaceful to their tank mates and very suitable for community tanks. Molly fish can be housed in a community aquarium that contains fish of similar size and temperament, as long as they share similar water requirements. So other livebearers like Guppies, Swordtails, Platies are the best tankmates. They all like alkaline water (pH 7-8).

They also live harmoniously with Zebra Danios, Minnows, Gouramis, Catfish, and Tetras such as Silvertip Tetras and Black Skirts. They do get along with Pleco fish, but, if you want to add Pleco fish, place only one. Since Plecos like algae, they may not leave very much for Mollies to eat.

Fish foods and feeding

Molly fish thrive on vegetable flake foods combined with either live or dried blackworms or bloodworms. Provide them with a diet high in algae content, including Spirulina-based flakes, as well as parboiled fresh vegetables, such as romaine lettuce, green peas, string beans and zucchini slices.

You should feed them two times a day. Don’t offer them more than the amount they can consume in 2-3 minutes. Uneaten food will compromise the water quality and return back to negatively affect the health of your fish.

Breeding Molly fish

Sexual determination

male-mollyMale molly with a large gonopodium

The male Mollies is easily distinguished from the female as the male Sailfin is usually smaller in size and much slimmer than the female, and has a large gonopodium. The male also has a sail dorsal fin which is absent in the female. The dorsal fins in males usually develop after two years of age.

Breeding the fish

breeding molly fish

Breeding can be accomplished if sufficient space is provided (20-gallon tank or larger) to facilitate the mating. Usually, it takes only 40 up to 70 days before the gestation period ends. There will be at least 20 live young Mollies in a female but sometimes she can have as much as 60 live young baby Mollies inside.

When the belly of the pregnant Molly is very distended, it is about to lay. Everything you need to do is creating a quiet place for the fish to give birth. The male Mollies and other fish in the community aquarium can cause stress on the pregnant fish if you don’t do any thing to protect the fish. Stressed pregnant mollies can cause more aborted births and stillborn.

You can use a breeding box or a separate tank to prepare for breeding Molly fish. By this way, you can protect the pregnant Molly as well as its baby fish. If you lay the female give birth in the community tank, your aquarium must have enough plants to provide hiding places for the little fish. They would eventually leave the plants if they are already big enough to swim and not to be eaten by other fish.

Caring baby Mollies

black-molly-giving-birthBlack Sailfin Molly giving birth in a breeding box

A single female can produce 20-60 baby Mollies once time. Once all the babies are born, transfer the female into a protected section of the main tank for it to rest as well as prevent the fish from eating its babies. The baby Mollies swim freely after birth and grow relatively quicker. They do need a lot of attention as they are easily prone to diseases.

The baby Mollies can be fed daphnia, egg yolk, newly hatched brine shrimp, or commercially prepared baby livebearer food. After a time, you can use tropical flakes or pellets to feed them until they get mature. Live fish foods like black worms, grindal worms, and blood worms help to boost the raising of baby Mollies. In nature, the primary food of Molly fish is algae, so you could add some aquatic plants to the fry tank to provide them a place for hiding as well as supply some vegetable foods. You should feed the baby fish just enough to avoid dirty water harmful for the fish.

Waiting until the babies get mature (it’s regularly around two months until they’ve doubled in size), introduce them into the community aquarium with the other larger fish. Remember to feed the fish in the tank before applying the new Mollies to ensure that they don’t think the new comers are foods you give them.

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4 comments

  1. My molly is black with small white spots and a bit of orange spots anyone know what type of molly that is?? Just wanting to know what type of molly I have.

    • Hi Jessica,
      The black molly with white spots is Dalmation Molly.

  2. when a lyretail Molly gives birth will the fry have lyretails when they are born or does the tail develope as they get older?

    • I doesn’t know because I only had round tail Mollies in the past.