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black molly

Black molly- the black beauty in the aquarium

Today we'll take a closer look at a species from the Poecilia family. Although its Latin name probably doesn't say anything to you, most of our audience knows this family very well- molly fish. Among a lot of colourful molly species of this family, there is one black sheep. Actually, not a sheep but a fish named Black Molly.


In nature, black molly fish occurs in Central and South America and other mollies. These tropical fish's natural habitat is mostly South America's freshwater streams. Still, sometimes they are observed in seas as they adapt to saltwater conditions. Despite this fact, they instead prefer freshwater habitats. Black molly catches the eye thanks to its unique colouration - entirely black. Thanks to it, it adds an exciting colour to each fish tank and contrasts with the surroundings.

Moreover, it is a vivacious and sociable freshwater fish that fits into a general, multi-species community tank. The community fish are ideal tank mates also because they feed on unwelcome algae. Although black mollies are not schooling fish, keeping a few of these individuals for a comfortable life is recommended. In aquariums smaller than 100l (so 270-gallon tank), it's better to keep one male and 4-5 females. Males of this species become very territorial, so even in the case of larger tanks, it's essential to have more females than males. Gender diversity is visible to the naked eye. Males have an anal fin modified to serve as a copulatory organ, known as a gonopodium. Moreover, male mollies are more petite than female molly fish, which grow to 8-10cm in the aquarium.



Now let's talk about black molly's requirements which should be considered before adding it to the current stocking. Firstly, this species is sensitive to water temperature changes, so starting from introducing it to the quarantine aquarium (which is highly recommended before putting it into a general fish tank because the fish may bring unwelcome infections from the fish stores), be super delicate. A quarantine aquarium is a separate tank where the new fish should stay in case of health problems. If it turns out that you bought a sick fish, the quarantine aquarium will prevent other fish from being infected. Depending on the black molly disease, the infected black molly should be separated from the other tank mates as long as the symptoms are visible. Among black molly diseases, fish pox and protozoan are common. You can try to use aquarium salt baths to treat them, not in the same tank but in a hospital tank.

For black mollies' best development, try to maintain a stable temperature between 24-28 degrees Celsius. They are tropical fish, so they prefer warmer water. For the substrate, gravel is recommended. Black molly likes hiding places, so decorations of stones and dense, fast-growing plants (e.g. Anubias) will be a great choice. We recommend adding some floating plants, e.g. Vallisneria, for a better arrangement effect.

On the other hand, it's a lively fish, so space to swim is essential. The good thing is that black molly likes to swim in the central and upper parts of the tank, so you can admire it almost constantly. The water should be very well filtered and oxygenated, pH 7-8, water hardness 11-30dGH. Poor water quality and unstable water temperature can lead to serious health problems in the case of black molly fish, so ensure you're equipped with a proper filtration system and aquarium heater if needed.


Functionality & Feeding

Black mollies are also considered easy to care for in the black molly diet. They clearly prefer plant food. As the black mollies feed mainly near the water surface, they should be provided with a light flake food with a total or high plant content that does not sink too quickly. While deciding on the ready food, look if there are any ingredients supporting the fish's immune system because, as mentioned before, they are sensitive to temperature changes. It's worth investing in high-quality flake food containing, e.g. spirulina. We're sure that experienced fish keepers can advise you with fish food's best brands. It is also vital that the fish are not overfed. Too much food harms the animals themselves and can also upset the entire ecosystem in the aquarium and cause, e.g. snail expansion or too many toxic substances in water that disturb the water parameters. Some fish keepers prefer to support black mollies diet with some frozen foods, e.g. Daphnia.


The next advantage of keeping this species in the aquarium is that it likes eating algae. As every species of the Cleaning Crew, it has its favourite ones. The black molly is really effective with cleaning green and brown algae, as well as diatoms. Moreover, the young individuals also feed on cyanobacteria, so if you struggle with them, think of young black mollies, which may be the rescue. Adult fish prefer cleaning green algae, supporting their diet with flake food.



If you want to breed mollies, as long as you maintain optimal water parameters, including suitable water temperature, aeration and purity, breeding Black Molly should not be difficult. Pregnancy lasts from 4 to 6 weeks, and as a result, 10 to even 60 individuals appear. Black Molly is a livebearer fish, which means that female molly gives birth to fully formed young and capable of independent living. Moreover, the fry grows quickly and is not difficult to raise. However, to avoid being eaten by other fish, the female should be separated from the rest - by putting in a breeding place or other breeding tank. The young fry of black molly fish is very sensitive to toxins in the water, so the breeding tank should also be equipped with a filtration system. How to feed young black mollies? You can provide them with the same food as adult mollies, as long as it is chopped.


As you can see, the Black Molly is a really nice fish for beginners and experienced fish keepers in the aquarium hobby. As we always underline, this popular freshwater fish can join your Cleaning Crew, helping to control the algae level and support the filter's work. It's a sociable fish, so it can be kept with almost every species which requires similar water parameters. In our opinion, the black molly is unique among other molly species. And contrasted with colourful other tank mates, will be a real star of the tank.