Black Molly Care and Breeding Guide

It is currently one of the most reared fresh water aquarium fish popular amongst hobbyists. For some it appears bizarre because of its black color and in fact you will not get in the wild because it gets its most of its characteristics in captive breeding. Just as the name suggests it is no wonder it is referred to as the Black Molly. Most people who come across it for the first time usually want to know why a fresh water fish would have such a distinctive black color. The explanation to this question lies in the skin of the fish. Usually, all mollies that are black suffer from a bizarre and serious skin pigmentation condition that experts refer to as melanism. This skin problem is a direct opposite of albinism which is characterized with a lack of pigmentation.

The black molly has a small body and mostly the male will grow to be 3 inches in length maximum while the female may add a few more inches to this when fully grown. The lifespan of the fish is usually dependent on how they are cared for in captivity. Under good conditions in captivity, the fish will live even to a maximum of five years.

Appearance of Black Molly

Black Molly

This fish is generally black in color the reason why it is named as the black molly. The fins, the eyes, and most other body parts are completely black. It is however important to note that this fish doesn’t appear in the wild as it is and you will not find in the wild. The male of the fish are usually smaller than the female. On average, the male will grow to a maximum length of 3 inches but the female may grow a little bit longer. There are chances for you to see a streak of yellow line on the fish that runs from the head to the dorsal fin. There are instances that you may also see some slight silvery color on the flanks of the fish.


Black molly has got a rather wide range of freshwater habitats in the wild and may be found on brackish, hard or saline water with varied temperatures. Please note that the black molly doesn’t appear in the wild and is itself a hybrid descent from various species Poecilia. Its ancestors though are said to have been native to the Southern parts of the United States, in Mexico, and other parts of Central America.

The fish is generally hardy and as long as the conditions in the tank are properly set for it, it will do well. Just ensure that the water you put it into is hard but and also rich in minerals. Never keep the fish in water that is clogged with ammonia or nitrates because this will simply just kill it! Change of water is therefore recommended regularly and the frequency by which you will be replacing the water in the tank will be dependent on the number of fish you have in the aquarium.

Tank Requirements

The fish needs sufficient room for it to live well in a tank setting and therefore having a tank that is at least 20 gallons is advised. Ensure that filtration is robust and frequent water changes are a must for the fish to survive. Never mix them with other species of fish that are too large and aggressive because they can easily be eaten by other aggressive fish.

Here below take a look at some of the important tank requirements that will help you set a tank for your black mollies:

  • A tank size that is at least 10 gallons is good but one that is even bigger is better.
  • Even though the fish is very hardy and will adjust to temperature changes setting the tank temperature to 72°F – 78°F is advised.
  • The pH of the water in the tank should range between 6.7 and 8.5.
  • The water hardness should be dGH 20-30.

Ensure water changes in the tank every week, it is recommended that you change a quarter of the water in the tank to rid any nitrates or ammonia that may be present in there. The fish is quite sensitive o such compounds and will easily die if this is not checked!


Black Molly is an omnivorous fish that will feed on all types of frozen, live and even artificial food. To help the fish cope better in the aquarium, offer it lots of vegetable fiber content such as algae and related vegies.  It is important for you to know that mollies in the wild usually have lots of algae in their diet. This therefore calls on the keeper to ensure that sufficient algae food is offered to them in the tank.

A quick glance at the foods to give the fish while in the tank:

  • Molly flakes (artificial fish food)
  • Squash, boiled cucumbers, lettuce leaves
  • As for live food, you can feed them blood worms, tubifex, and brine shrimp
  • Just don’t forget to also include vegetable content in the diet too


Molly Fish are so easy to distinguish between the sexes and the females appear somewhat larger with visible rounded abdomen. The most striking feature you will be able to use to identify the female and male fish is the anal fin. The male fish has an anal fin that is shaped like a tube while the female’s anal fin looks triangular.

Breeding the fish is quite easy compared to other types of fish that are usually kept in the tank. Unlike many other fish that lay eggs to be fertilized outside the body during spawning, molly fish are live breeders. This is to mean that the juvenile fish are spawned live by the female instead of being hatched outside the body. There are no special tank conditions needed for the fish to breed their young ones. What you may have to do is simply to keep the female and the males just in one tank to facilitate the breeding process.

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