Molly Fish Care – A Complete Guide

Fish keepers often see many molly fish in fish stores. As they are found in most home aquariums, and they are easy to care for. Moreover, they require no special or hard treatment, and they are easy to keep for beginners.

Molly fish care requires you to know the basics, in terms of their tank requirements, appropriate feeding, and maintaining a clean environment, to ensure optimum health, and extend their lifespan.

This article is a comprehensive compilation of research concerning caring for molly fish. Moreover, other important information, that pertains to the well-being of molly fish are discussed.


Molly fish are freshwater habitats that belong to the family, Poeciliidae. However, in the genus Poecilia, there exist 40 species, whereby, 39 of them are mollies, while the remaining one is known as Endler’s livebearer. Also, mollies are native to Americans, but you can find them in various locations.

However, something interesting about mollies is the fact that they don’t lay eggs, they rather give birth to their children’s lives. Just like guppies, they are referred to as livebearers. Mollies are good options for beginners, as they are hardy and easy to care for.  Moreover, they can survive in a community tank, especially among species that similar traits. Also, if you breed them properly, they can live for five years.

Types of Molly Fish

There are various types of molly fish that exist. However, there are two major types of mollies you will find in most aquariums. They are, sailfin mollies (poecilia latipinna), and short-finned mollies (poecilia sphenops). These two species are the most common in aquarium tanks because they are easy to keep. However, short-finned mollies are easy to keep than sailfin mollies. Sailfin mollies require a harder steady water temperature and more water volume. Moreover, here is a list of various molly species.

Molly Fish Care Guide

Mollies are adaptable, easy to the cafe for, and hardy species. Just like most fish, mollies require a clean tank to stay healthy. To be a successful fish-keeper, you need to observe clean hygiene and maintain regular cleaning. Moreover, make sure the water condition is normal. And the ammonia and nitrite level is accurate.

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Also, there is a common disease that happens to most mollies. It is referred to as, “molly disease” or “shimmies”. However, the major cause of this disease is unclean water or an unhealthy environment. Moreover, you will know if your fish is affected, by observing if there is a change in movement. A fish that has been infected, will swim less actively, and movement will be in one position. Therefore, you check your water condition and correct any change that influences the disease. Other symptoms of diseases that could infect mollies include; dark spots, loss of appetite, wounds, inactivity, and color change.

Molly Fish Appearances

There are many varieties of molly fish. However, the most common molly is poecilia sphenops. In most cases, differences are seen in mollies color and pattern. Sometimes, you can also spot some differences in their body size and shape. The common molly often has a flat body, long at the center, and narrow close to the mouth region. Also, the caudal fin is positioned at the end, which may be colorful or transparent, and appears as a large fan. However, the dorsal fin can be misplaced as the caudal fin. As it also appears like a fan, but it is usually flattened to the fish’s body.

Moreover, breeding mollies is easy, as it is not hard to differentiate the female and male mollies. Usually, the female’s anal fin spreads across like a fan, whereas, the male anal fin is often pointed. Also, the females are larger in body size, reaching up to 4.5 inches. While the males grow to an average of 3 inches. As for pregnant female mollies, they often appear larger, and their belly swollen than other females in the tank.

Mollies Behavior

Mollies are peaceful fish, but they can be somewhat aggressive when they feel they are being threatened in their tank. Sometimes, they can also be aggressive when they try to fight for dominance, or when the males are fighting for the attention of a female. There you need to provide suitable tank mates that mollies can withstand, and also provide enough space for them to move freely. As this will prevent harm, especially in cases where the fish for territory.

Also, mollies are usually very active and happy. They enjoy being schooled together. However, ensure the females outnumbers the males in the tank. As the males sometimes harass the female, and she gets to feel lonely. However, the active nature of mollies will help you, by making it easy for you to spot and recognize each fish’s personality.

Suitable Water Quality for Mollies

Mollies are well known for being hardy. However, make sure their environment condition is optimum for their keeping. Ideally, their water temperature should be between 72-80 degrees Fahrenheit. Also, you should keep the water temperature steady, to avoid stressing the fish. Although, mollies can easily adapt to different water conditions. But they thrive best in heavily filtered water. Generally, we recommend that you change at least one-third of your aquarium water, every week.

Naturally, mollies are freshwater species, but they also live in salty or brackish water. Most mollies can survive in freshwater. Although, some aquarists prefer to add salt to their aquarium water. Regardless, just a teaspoon of aquarium salt is suitable for one gallon.

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Molly Fish Tank Size

The tank size for keeping molly fish is majorly dependent on the molly’s size, and the quantity of fish to live inside. For example, large species like tailfins will require at least a 30-gallon size. However, an average molly will need at least a 10-gallon tank.

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Molly Fish Tank Requirements

Setting up an aquarium tank for mollies is quite easy. Because you need not bother about setting various environment conditions for different species. As all mollies require the same tank setup, even with those you capture in the wild.

Firstly, you need to set up a layer of the sandy substrate at the bottom of the tank. Also, provide fine grains that will provide supports for the plants. However, there are various plant options you can choose from, but we recommend that you go for taller plants like, Anubias nana, which will serve as good shelter support. Also, you should create crevices and caves, by using decorations, like rocks. However, these rocks will provide hiding space for fish that are being harassed by other fish in the tank. Especially, the female fish.

For the temperature, hardness, and PH requirement, mollies require 72-80°F, 20-30KH, and 7.0-8.5 respectively. However, you need to install a heater in the aquarium tank, to help maintain the temperature level. Also, you need to just provide standard aquarium lighting to add the excess to your tank set up. Moreover, it is important you also provide a filter. Mollies can be sometimes messy, and it will be difficult to clean the tank without the use of a filter. And remember, maintaining a clean environment, will help your fish in reaching an optimum state of health.

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Maintaining and Cleaning Your Molly Tank

Most aquarists often make use of a “water changer”, or filter. As this will make fish keeping an easier task for you, and more fun. Moreover, using a water changer is not difficult to apply. As all you need to do is attach it to your faucet. However, it comes with a switch that pulls out the water through the hose. Meanwhile, when you are about filling the aquarium with new water, just on the switch. Also, you should use a heater to keep the water temperature steady.

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Molly Fish Habitat

Molly fish are not only seen in home aquariums; some also exist in the wild. Also, for molly fish you get to see in the wild, you can be certain they have no specific habitat. However, there are certain environmental conditions that they will rather prefer to stay in. Whereas, in most cases, they are left with little or no choice. Because, they are more strong-headed, as they have lived in several water conditions. From a likely tolerance to brackish waters, then high hydrogen sulfide levels. However, you can find them in shallow areas of rivers, small streams across South and North America. You will most likely find them if you suspect an area is sandy with rocks, and debris found on top.

Usually, their habitat is of the tropical climate, as it enhances the supply of light. Also, the water is often water and flows slowly in one direction. More so, they thrive best in a slightly alkaline PH environment. Often, plants grow well in their habitat, as it serves as a shelter for them, and also enhances reproduction.

Molly Fish Tank Mates

Mollies can survive in a group of four species. Peaceful species, mollies naturally stick together, and they do not cause harm when you keep them in a community tank. Also, they enjoy the company of one another. Regardless, they exhibit aggressive traits mostly for reproduction. So, it will be to keep more females than males, in a tank. However, there are a lot of fish species to choose from, especially the small peaceful ones. Some compatible tank mates are; Platies, Harlequin Rasbora, Cherry Barbs, Dwarf Gourami, Corydoras Catfish, Rosy Barbs, Zebra Loaches, and Yo-yo Loaches.

Moreover, you need to avoid large and aggressive fish, as they may fight your mollies, and stress them out, which may, in turn, lead to death.  For example, Cichlids. Especially, Convict cichlids. As they have records of not relating well with other species and a reputation for aggressive behavior. Although, some cichlids, such as Angelfish, are an exception.

Feeding Molly Fish

Molly fish being omnivores, makes their choice of food varies widely. Moreover, this will make feeding them easy, as there are various types of food you can feed them. However, wild mollies feed on small invertebrates, by eating mostly algae and plants. Also, you can feed them vegetables from your meal. Ensure that the vegetable has no spices that have been added to it. However, these vegetables include zucchini, spinach, and lettuce. Moreover, these foods are a good option to consider, to add to your home aquarium. However, you can use these food items to create your own homemade fish foods.

You should provide a wide range of nutrients, by adding some artificial foods such as pellets and flakes. Moreover, you can also supplement it with other food options, to improve diet diversity. Therefore, you should include other sources of protein together diet. These include live and frozen foods, brine shrimps, and bloodworms. Moreover, concerning the frequency of feeding, feeding them twice daily is good for their growth. Avoid feeding them too much at a time, as the digestive system will not have enough time to process the food. Also, you should grind the babies’ food before serving them, so they can easily chew on the foods. You can start serving them adults food when the baby’s mouth is as big as that of adults’.

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Molly Fish Breeds

As said earlier, Molly fish are livebearers. That is, they don’t lay eggs. They rather give birth to their young alive. Moreover, mollies are one of the easiest fish you can capture, and they will mate frequently. However, apart from the natural frequent breeding nature of mollies, you need to make sure the tank requirements are in constant shape, and you also keep the environment, and water clean. Because female mollies can prevent themselves from getting pregnant. Especially when the environment condition is not favorable or appropriate for breeding. As a result, they see this as a threat to their lives, and that of their fry.

You can initiate mating by raising the temperature slightly above normal. Although, you shouldn’t let this exceed 80°fahenreit. Moreover, mating occurs when the male molly displays his courting attitude, while the female mollies agree to it by allowing the male to fertilize. her eggs. Although, the male sometimes fertilizes her eggs when she is unaware, by copulating with her from behind. Usually, the female often prefers to copulate with the largest male. Also, female mollies can release a large number of fry at a time. Especially the large female mollies. As they can release up to 100 fry at a time. In most cases, it takes 35-45 days, after fertilization, for the other to give birth to her babies.

However, as soon as the female molly gives birth, you should separate the babies from their mother. This is to make certain that they don’t die young, and they live to adulthood. One strategy you can implement is placing the pregnant mollies in a breeding box and allowing the fry to escape through a small hole, while the mother gets trapped in the breeding box.

Molly Fish Diseases

Here are some diseases that are particular to freshwater habitats.

  • Shimmy: Shimmy is the most common symptom that occurs in molly fish. Whereas, shimmy is an early sign that result in several possible diseases. However, you can treat this by giving your fish molly bright medication.
  • Lethargy: Lethargy is another form of the disease you may observe in your female molly. While, in most cases, it comes along with the pregnancy situation. Just as female humans.
  • Torn Fins: Torn fins can either result from fin rot or a fight. Also, make sure to confirm if it is a fungal or bacterial infection before treatment.
  • Reddened/purple gills: When the gills of your fish are often with red or purple coloration, it shows a sigh of nitrate or ammonia poisoning. In this case, you need to immediately change the aquarium water. As ammonia poisoning often results from poor water conditions. Moreover, this will be easier with the use of a heater, and filter.
  • Pop Eye: The pop eye is usually a symptom of several possible diseases. Including the dreaded disease – fish tuberculosis. However, causes of pop eye are; damage from the fight, aquarium accident, water pollution, ammonia poisoning. Also, the pop eye rarely results from oxygen oversaturation.
  • Ich: Grain-like white spots are a symptom of ich. You can treat this by getting medication from a fish store.
  • Dull white film on skin: This spot could either be oodinium or fungal infection. However, you can determine by turning off the tank light, and shining a torch on the fish. So, if the white film glows back, it shows its oodinium. While it’s a fungal infection if you see a white patch that appears like a mold.

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No specie of molly requires different special care from another. In most cases, the difference is dependent on the number of molly fish in the tank, and the age of the molly fish. For instance, a larger quantity of fish will require a larger gallon size. And you should separate mollies babies from a community tank until they are big enough not to fit into the adult mollies mouth.