Molly Fish: Ultimate Guide (Care, Diet, Breeding & More)

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Written By Matt Stevens

Hi, I'm Matt! I've been obsessed with fishkeeping for over 15 years now and created this site to share my knowledge with others.

Molly Fish are a highly attractive species of fish, which explains why they’re so popular in the aquarium community.

When it comes to freshwater aquarium fish, they are among the top choices. It is incredibly easy to take care of them, and they have a wide range of species as well.

Generally, you will have no trouble at all in caring for your Mollies, but it is best to know all about their species and the care they require. If you look after them the right way, they will always be happy and healthy, and also live a long life.

If you want to find out all about these fish, you don’t need to worry. We have created a resourceful guide that teaches you how to care for your Molly Fish, including their habitat, water requirements, diet, tank mates, breeding, and much more.

Species Overview

Molly Fish belong to the Poeciliidae family and have the scientific name Poeciliasphenops. If you have ever been to pet stores or aquariums in public spaces, you may have seen them at least once. They are some of the most popular freshwater species you can find.

Plus, Mollies are suitable for beginners who are looking to buy their first aquarium, as well as aquatic experts.

Life Span3-5 years
Color FormVarious
Care levelEasy
CompatibilityPeaceful fish
Size4-4.5 inches
Tank SetupFreshwater: rocks and caves
Minimum Tank Size10 gallons

They are also known to be peaceful and adapt well to different types of tanks and water conditions. Moreover, they are some of the best choices if you want to keep different species of fish in the same tank.

Molly Fish are native to the tropical rivers of North and South America, where you can find slow-moving waters and loads of vegetation.

Ever since they have become a staple of the aquarium community, many breeders and aquatic experts have cross-bred them with other species. Therefore, you can find many different colors and species of Molly Fish.


Molly Fish have an average lifespan of 3-5 years if they live in aquariums. You can prolong their lifespan by maintaining the water conditions regularly, and it also depends on the species you get.

Luckily, they are quite easier to take care of, and you won’t have to worry about anything if you follow our guide.


Since there are several species and types of Molly Fish, they have different appearances as well. Some of them also resemble the Common Molly, which is another species of fish.

Molly Fish have a slim and flat body and a triangular-shaped head. Their body is wider in the middle, whereas their snout is much narrower. Moreover, their body grows slimmer towards their fan-shaped tail.

You can easily identify male and female Molly Fish with their appearances. Male Molly Fish are quite smaller than their female counterparts and have a pointed anal fin. The female fish have a broad and fanned anal fin.

Moreover, female Molly Fish have a noticeable gravid spot, which grows during pregnancy and is also used to hold their babies.

Types of Molly Fish

According to aquatic experts, there are roughly 39 different species of Mollies out there. Since we can’t mention all of them, let’s have a look at the most popular species.

1.     Black Molly Fish

These species have a pure black body, and you may find a tinge of orange or yellow on their fins. Their dark appearance makes them strikingly beautiful.

2.     Sailfin Molly Fish

Sailfin Molly Fish have a similar body, but they have a taller dorsal fin stretching to the tip of the tailfin. They come in several colors, including black.

3.     Balloon Molly Fish

Balloon Molly Fish are given this name because they have a rounder belly than other Molly Fish, even when they aren’t pregnant. They are also available in several colors.

4.     Lyretail Molly Fish

Lyretail Molly Fish are known for their beautiful tailfin, which have a similar shape to other fish. Plus, they have long rays at the top and bottom.

5.     Dalmatian Molly Fish

The Dalmatian Molly Fish are highly popular. They have white bodies with specks of black on them, which makes them resemble Dalmatian dogs. You can find this pattern on standard Molly Fish, as well as Lyretail, Balloon, and Sailfin.

6.     Gold Doubloon Molly Fish

The Gold Doubloon Molly Fish are also popular among aquarium owners. The front of their body is bright yellow, while the lower half is black.


An adult Molly Fish can grow up to 4-4.5 inches at best, which allows you to keep them in smaller aquariums.

However, if you have Sailfin Molly Fish, they can grow a few inches more than the other species, mostly 5-6 inches in length.

Molly Fish Care

As we mentioned above, it is quite easy to take care of them in your aquarium, even if you are new to fish care. If you keep following the care guidelines that we provide you with, your Molly Fish will be in good hands.

Tank Size

Since Molly Fish achieve a maximum length of 3-4 inches, you can easily keep them in small and medium-sized tanks. Most of the species will thrive in a 10-gallon tank.

In fact, a 10-gallon fish tank is suitable enough to accommodate four Molly Fish, but this doesn’t mean that you should stick to this size. A slightly larger tank would be better for them.

If you plan to house a larger amount of fish, you need to add three gallons of capacity per Molly Fish.

However, if you plan to keep Sailfin Molly Fish, then you may need a larger tank since they tend to be longer than other species. Therefore, you need to have a 30-gallon tank for them.

Water Parameters

Molly Fish have quite a different habitat in the wild. Mostly found in rivers, they are known to swim towards salty waters and oceans for short periods of time. However, this doesn’t mean that you need to add salt into the aquarium waters.

Generally, they are quite adaptable and peaceful. They prefer warm waters with a neutral pH and a high level of hardness.

The water parameters for Molly Fish differ from species to species, but you can maintain a water temperature between 72°F to 78°F, with 80°F for only a few species. Plus, you should keep the pH level between 7.5 and 8.5 and the water hardness between 20 to 30 KH.

The key is to monitor the water conditions periodically. To do this, you should get a good-quality water testing kit so that you can adjust the water conditions if needed.

What to Put in Their Tank?

Mollies are more comfortable living in an aquarium that emulates their natural habitat. This translates to lots of vegetation and hiding places.

Firstly, you should place sand or gravel substrate at the bottom of the bank, which would help in keeping the places in their place. Since Molly Fish spend most of their time in the upper and middle levels of the tank, they won’t have to do much with the substrate.

Once you have added the substrate layer, you can add live plants to the tank. You can add a mix of long and short plants like Anubias and Java fern, among other plants.

Apart from these, you can also add several accessories like rocks, driftwood, and caves for the fish to hide in. Not only do they serve as hiding places, but they also provide fish with algae to munch on.

Molly Fish don’t need any special lighting to thrive, so you can install standard lighting above their tanks. The light is also good for the plants to stay healthy and grow.

You will also need to install a quality filtration system since all species of Molly Fish tend to produce a lot of waste. If the waste isn’t filtered out, it will raise nitrate and ammonia levels in the water.

For this purpose, you need a strong bio media filter, along with internal or external sponge filters.

Common Diseases

Mollies can also suffer from diseases like other fish, and some of the unique diseases include Molly disease and constipation.

Molly disease is also called the ‘shimmies,’ and it is caused by unsuitable water conditions. For instance, if the water temperature changes drastically or the level of ammonia in the tank rises, it can cause them to suffer from this disease.

Molly Fish who have the disease can’t swim properly and are known to wiggle while staying in one place. However, you can treat them by changing the water regularly, which keeps ammonia and nitrate levels in check.

Constipation is a disease suffered by Balloon Molly Fish, whose body shape causes their organs to be compressed. Overeating or quick eating can result in constipation, which can prove dangerous for them.

Apart from these, they can also suffer from common diseases, as well as parasites, flukes, bacterial infections, etc.

What Do Molly Fish Eat?

Molly Fish are known to consume plant-based foods, and they also munch on algae from time to time. Apart from this, they can also consume lettuce, spinach, zucchini, and other blanched vegetables.

Since they are also omnivores like many other fish, they enjoy high-protein snacks. You can feed them live or frozen foods, like brine shrimp, bloodworms, daphnia, and several others.

Make sure to provide your fish with live foods from time to time, as they play a major part in fulfilling their nutritional requirements. For convenience, you can add flakes and pellets to your Molly Fish diet, provided that they come from reliable brands.

Behavior & Temperament

Molly Fish are quite easygoing and peaceful, and they also get along with other fish. Since they are shoaling fish, they need a group of at least four or five fish in order to feel comfortable in their habitat.

However, you can also place them with a larger number of fish. They will swim around in a formation and explore every nook and cranny of the fish tank. Then, they will disband and start doing their own thing.

One thing you should take care of is that the number of male Molly Fish isn’t higher than the number of females. Males tend to trouble the females, especially if the conditions are perfect for breeding.

Although male Mollies aren’t violent or aggressive, they can intimidate the females with their behavior. This is why you should consider keeping the ratio of males to females tilted towards the female side.

Molly Fish Tank Mates

Since Molly Fish get along with several other species, you won’t have any trouble setting up an aquarium with different types of fish.

As long as you choose other fish that are peaceful and about the same size as them, Molly’s will cohabitate with them easily.

For this purpose, you should avoid any fish that is known to be aggressive or is significantly larger than the Molly because they might get preyed on if this happens.

You have quite a few options to choose from, which include:

Apart from these species of fish, you can also keep Molly Fish with freshwater aquarium snails and shrimp, such as the Cherry Shrimp.


The Molly Fish breeding process is fun to follow, and they are known to spawn a lot of babies as well. Healthy female fish can lay eggs quite a few times during their lifespan.

The best part is that you don’t need to do anything to get Molly Fish to mate. The female fish are livebearers, so they hold eggs in their belly until they are ready to hatch.

This means that when the fry are hatched, they are released into the water. However, if you want to ensure that you breed healthy fry, make sure to prepare a healthy and controlled environment. To do so, you can get a separate breeding tank and set the water to 78°F.

Females choose to breed with the largest male, so you can place the pair in the breeding tank. The mating process begins when the male starts to court the female. Then, the female lets the male fertilize her eggs.

When the fertilization is complete, the stomach of the female Molly Fish starts to grow in size, and you have to wait at least 45 days before the fry start to hatch. When the waiting period has passed, you should transfer the female to a breeding box.

One thing that you need to know is that Mollies aren’t protective of their babies, which is why they might try to eat their fry. Therefore, the breeding box will allow the female fish to release the fry through its lower part and also keep her separated from them.

As fun as the breeding process may seem, you have to be prepared as well. Molly’s can spawn as many as 100 fry in one go, so you will have to be prepared for the swarm of fish. You may need to shift the new fry into a separate tank and feed them powered fish food.

Once the babies grow a little, you can start feeding them baby brine shrimp until they reach their full size. If you are going to keep the fish you have bred, you will need a much bigger aquarium or several smaller ones.

Final Thoughts

According to aquatic experts, Mollies are some of the easiest fish to take care of. This makes them perfect for beginners too.

They are highly popular in the aquarium community, which is why you can easily find them at your nearest pet store or online as well.

Not only that, but they look wonderful swimming around in the aquarium, and you will be delighted to see them every time you walk by the tank.

There is nothing better than to have pet fish that don’t burden you with care instructions and water requirements. Molly Fish care will quickly become a part of your daily routine.