Molly Fish Care Guide: Everything You Need to Know

If you’re looking for a beautiful and easy-to-care-for fish, then Molly fish might be just what you need. These fish are known for their vibrant colors and peaceful temperament, making them a popular choice for both beginner and experienced fish keepers. In this article, we’ll provide you with a comprehensive guide on how to care for your Molly fish, so you can enjoy their beauty for years to come.

Molly fish require a clean and spacious tank, proper water temperature and chemistry, and a varied diet with high-quality food. Avoid overfeeding and provide hiding places. Monitor for signs of illness such as lethargy or abnormal swimming behavior. Consult with a veterinarian or experienced aquarist for advice on proper care.

As an avid fish keeper myself, I can attest to the joy that comes with owning Molly fish. These fish are not only stunning to look at, but they also have unique personalities that can make them a joy to watch. However, caring for them does require some knowledge and effort, which is why we’ve put together this guide to help you provide the best possible care for your Molly fish.

In this guide, we’ll cover everything from setting up the perfect tank environment to feeding and breeding your Molly fish. Whether you’re a first-time fish keeper or an experienced hobbyist, there’s something for everyone in this guide. So, let’s dive in and learn all about Molly fish care!

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Key Takeaways

  1. Molly fish are a popular and easy-to-care-for freshwater fish species that come in a variety of colors and patterns.
  2. To keep your molly fish healthy, it’s important to maintain suitable water parameters, including a temperature of 72°F to 78°F, a pH of 7.5 to 8.5, and a hardness of 20 to 30 dGH.
  3. Molly fish are omnivores and can be fed a variety of foods, including flakes, pellets, and live or frozen foods.
  4. The minimum tank size for molly fish depends on the number of fish you have, with 10 gallons recommended for 1 to 2 mollies and 20 gallons for 3 to 4 mollies.
  5. To set up a suitable tank for mollies, you’ll need equipment like an aquarium, a filter, a heater, lighting, substrate, and decorations.
  6. To maintain water quality, it’s important to perform regular water changes, with a frequency of weekly to bi-weekly depending on the size of your tank and the number of fish you have.
  7. Molly fish are peaceful fish that can be kept with other community fish species, but they may become aggressive towards other molly fish or similar-looking fish.
  8. Molly fish are livebearers and can give birth to many fry at a time, so it’s important to provide proper care for the fry once they’re born.
  9. Overall, molly fish are a great choice for beginner fishkeepers and can provide years of enjoyment with proper care and attention.

Species Summary

If you’re interested in keeping Molly fish, it’s important to understand their basic characteristics. Here’s a brief overview of everything you need to know about these fascinating fish.


Molly fish are native to the freshwater streams and coastal brackish waters of Mexico, Central America, and South America.

They were first introduced to the aquarium trade in the early 1900s and have since become one of the most popular species among hobbyists.


Molly fish are known for their unique and striking appearance. They come in a variety of colors and patterns, including black, gold, silver, and orange.

They are also characterized by their large dorsal fins and fan-shaped tails.


Molly fish have a relatively long lifespan compared to other freshwater fish, typically living for three to five years in captivity.


On average, Molly fish grow to be between two and four inches in length. However, some species can grow up to six inches in length.

Growth Rate

Molly fish are known for their rapid growth rate, especially during the first few months of their lives. With proper care and nutrition, they can reach their full size in just a few months.

Behavior & Temperament

Molly fish are generally peaceful and easy to care for, making them a great choice for beginners.

They are also known for their playful and curious personalities, often interacting with their owners and other fish in the tank.

However, it’s important to note that male mollies can sometimes exhibit aggressive behavior towards each other.

Personally, I’ve found that Molly fish are some of the most entertaining and engaging fish to keep. I love watching them swim around their tank and interact with each other.

With a little bit of knowledge and effort, anyone can enjoy the beauty and charm of these fascinating fish.

Tank Setup for Molly Fish

AquariumProvides a home for your molly fish
FilterHelps to maintain water quality
HeaterMaintains a consistent water temperature
LightingProvides a day/night cycle for your fish
SubstrateProvides a natural environment for your fish
DecorationsProvides hiding places for your fish

Tank Size

The first step in setting up a tank for molly fish is choosing the right size. I recommend a minimum tank size of 20 gallons for a small group of molly fish.

This will provide enough space for the fish to swim and grow comfortably. Keep in mind that mollies are active swimmers, so a larger tank is always better.


Molly fish do not require any special lighting, but it is important to provide a consistent light cycle to mimic their natural environment.

A timer can be used to ensure the tank light is on for 8-10 hours per day.


Good filtration is essential for keeping the tank clean and healthy for your molly fish. A hang-on-back filter or a canister filter is recommended for a 20-gallon tank.

Make sure to clean the filter regularly to maintain its efficiency.

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Aeration is important for maintaining oxygen levels in the tank. A simple air stone or sponge filter can be used to provide sufficient aeration for your molly fish.


Molly fish are tropical fish and require a consistent water temperature of 75-80°F.

A heater is necessary to maintain the proper temperature in the tank. Make sure to choose a heater appropriate for the size of your tank.


Adding decorations to the tank not only makes it more aesthetically pleasing, but also provides hiding places for your molly fish.

Driftwood, rocks, and caves are great options for decoration.


Choose a substrate that is suitable for your molly fish.

Sand or fine gravel is recommended as it allows the fish to sift through the substrate in search of food.


Live plants not only enhance the appearance of the tank, but also provide a natural habitat for your molly fish.

Java fern, Amazon sword, and Anubias are great options for beginners.

In conclusion, setting up a tank for molly fish requires careful consideration of tank size, lighting, filtration, aeration, heater, decoration, substrate, and plants.

By following these guidelines, you can create a healthy and comfortable environment for your molly fish to thrive.

Personally, I have found that adding live plants to my molly fish tank not only helps to maintain water quality, but also provides a more natural and visually appealing environment for my fish to live in.

Water Quality

Water ParameterIdeal Range
Temperature72°F to 78°F (22°C to 26°C)
pH7.5 to 8.5
Hardness20 to 30 dGH

One of the most important aspects of Molly fish care is maintaining good water quality. Poor water quality can lead to stress, disease, and even death in your fish.

In this section, we’ll cover the three main factors that affect water quality: water temperature, pH, and hardness.

Water Temperature

For optimal health and growth, Molly fish require a water temperature between 75-82°F (24-28°C).

It’s important to keep the water temperature consistent, as sudden changes in temperature can cause stress and illness.

To maintain a consistent temperature, consider using a heater and thermometer in your aquarium.

Water pH

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Molly fish prefer a slightly alkaline water pH between 7.5-8.5. It’s important to monitor the pH regularly and make adjustments as needed.

If the pH is too low, consider adding a pH buffer to raise it. If the pH is too high, consider adding driftwood or almond leaves to lower it naturally.

Water Hardness

Molly fish prefer moderately hard water with a hardness level between 10-20 dGH. If your water is too soft, consider adding a mineral supplement to increase the hardness.

If your water is too hard, consider using a reverse osmosis filter to lower the hardness.

Personally, I had a difficult time maintaining good water quality when I first started keeping Molly fish.

I didn’t realize how important it was to monitor the temperature, pH, and hardness regularly.

But once I started paying closer attention to these factors, my fish became much healthier and happier.

How Often to Change Water in Molly Fish Aquarium

Weekly25% to 50% of the water volume
Bi-weekly50% of the water volume

Changing water in your molly fish aquarium is an essential part of maintaining a healthy environment for your fish.

It helps to remove harmful toxins, debris, and waste products that can accumulate in the water over time. Here’s what you need to know about how often to change water in your molly fish aquarium.

As a general rule, you should aim to change 10-20% of the water in your molly fish aquarium every week. This will help to keep the water clean and clear, and prevent the buildup of harmful toxins.

If you have a heavily stocked aquarium or a particularly messy fish, you may need to change the water more frequently.

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It’s important to note that you should never change all of the water in your molly fish aquarium at once, as this can disrupt the delicate balance of the ecosystem and harm your fish.

Instead, aim to change a portion of the water each week, gradually replacing the old water with fresh, clean water.

When changing the water in your molly fish aquarium, it’s important to use a water conditioner to remove any chlorine or other harmful chemicals that may be present in your tap water.

You should also use a gravel vacuum to remove any debris or waste products that have accumulated on the bottom of the tank.

Personally, I have found that changing 10% of the water in my molly fish aquarium every week works well for me. It keeps the water clean and clear, and my fish seem to be healthy and happy.

However, every aquarium is different, so it’s important to monitor your water quality and adjust your water change schedule as needed.

Molly Fish Diet

FlakesTetraMin Tropical Flakes, Hikari Micro Pellets
PelletsNew Life Spectrum, Omega One
Live/Frozen FoodsBloodworms, brine shrimp, daphnia

What to Feed?

Molly fish are omnivores, which means they eat both plants and animals. In the wild, they feed on algae, small insects, and other aquatic creatures.

In captivity, they can be fed a variety of foods, including flakes, pellets, freeze-dried or frozen foods, and live foods.

Personally, I like to feed my Molly fish a mix of high-quality flakes and frozen brine shrimp. I find that this combination provides them with the necessary nutrients and keeps them healthy and happy.

How Often?

Molly fish should be fed 2-3 times a day, but only what they can eat in a few minutes. Overfeeding can lead to health problems, such as obesity and constipation.

It’s important to remember that fish have small stomachs and can only eat a limited amount of food at a time.

I usually feed my Molly fish once in the morning, once in the afternoon, and once in the evening. This gives them a consistent feeding schedule and helps prevent overfeeding.


Vary their diet: Feeding your Molly fish a variety of foods will help ensure that they receive all the necessary nutrients.

Don’t overfeed: As mentioned earlier, overfeeding can lead to health problems. Make sure to only feed them what they can eat in a few minutes.

Clean the tank: Uneaten food can quickly pollute the water, so make sure to remove any excess food after feeding.

Consider live foods: Live foods, such as brine shrimp and bloodworms, can provide your Molly fish with a more natural diet and can be a great source of protein.

In conclusion, feeding your Molly fish a balanced diet is essential for their health and well-being. By following the tips above and providing them with a variety of foods, you can ensure that your fish are happy and healthy.

How Many Molly Fish Should Be Kept Together?

Number of Molly FishMinimum Tank Size
1 to 210 gallons
3 to 420 gallons
5 to 630 gallons

When it comes to keeping Molly fish, it is important to consider the number of fish that should be kept together in a tank.

While Molly fish are social creatures and can live in groups, overcrowding can lead to stress, aggression, and even death.

A good rule of thumb is to keep one male Molly fish with two to three female Molly fish in a 10-gallon tank.

It is important to note that male Molly fish can be aggressive towards each other, so it is best to keep only one male in the tank.

Additionally, if you have a larger tank, you can keep more Molly fish, but make sure to provide enough space and hiding spots for each fish.

Personally, I started out with three Molly fish in a 10-gallon tank, and they seemed happy and healthy.

However, as they grew, I noticed some aggression between the male fish, so I added more female fish to the tank.

This seemed to help balance out the aggression, and all of the fish have been thriving since.

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Overall, it is important to consider the size of your tank and the number of fish you have when deciding how many Molly fish to keep together.

By providing enough space and companionship, you can ensure that your Molly fish live happy and healthy lives.

Common Diseases

As much as you want your Molly fish to be healthy, there may be instances where they can get sick. Here are some of the common diseases that your Molly fish may encounter:


One of the most common signs that your Molly fish is sick is when they start to lose their appetite. They may also become lethargic and less active than usual.

You may notice that they are not swimming as much as they used to or that they are hiding more often.


There are several causes of diseases in Molly fish. One of the most common causes is poor water quality.

If the water in your aquarium is not clean, it can lead to bacterial and fungal infections. Another cause of diseases is overcrowding.

If you have too many fish in your aquarium, it can lead to stress and an increased risk of diseases.

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If you notice that your Molly fish is sick, it’s important to act quickly. The first step is to isolate the sick fish from the others to prevent the spread of the disease.

You can then treat the fish with medication, which can be purchased at your local pet store.

Follow the instructions on the medication carefully to ensure that your fish recovers quickly.


The best way to prevent diseases in your Molly fish is to maintain a clean and healthy aquarium.

Make sure that you clean the tank regularly and that the water quality is good. You should also avoid overcrowding the aquarium and ensure that the fish are getting a balanced diet.

Regularly monitoring your fish and their behavior can also help you catch any potential diseases early on.

Personally, I had an experience where one of my Molly fish became sick due to poor water quality.

I noticed that it was not swimming as much as it used to and was hiding more often. I immediately tested the water and found that the ammonia levels were too high.

I did a water change and added some aquarium salt to the tank. Within a few days, my fish started to recover and was back to its active and healthy self.

Signs of Healthy Molly Fish

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As someone who has kept Molly fish for a few years now, I have learned that keeping them healthy requires a bit of knowledge and attention to detail. Here are a few signs that your Molly fish are healthy:

  1. Active swimming: Healthy Molly fish are active swimmers and will often swim around the tank. If your Molly fish are lethargic or not swimming around as much, it could be a sign of illness.
  2. Bright colors: Molly fish come in a variety of colors, but healthy fish will have vibrant and bright colors. Faded or dull colors could be a sign of stress or illness.
  3. Clean fins and scales: Healthy Molly fish will have clean and clear fins and scales. If you notice any discoloration, spots, or growths on your fish, it could be a sign of a bacterial or fungal infection.

It is important to note that these signs are not foolproof and should be used in conjunction with other indicators of fish health.

Additionally, it is important to regularly test the water in your tank and maintain proper water parameters to ensure the health of your fish.

In my experience, keeping Molly fish healthy requires a bit of effort, but the rewards are worth it.

By paying attention to the signs of healthy fish and maintaining a clean and healthy tank environment, you can enjoy your Molly fish for years to come.

Signs of Sick Molly Fish

As a fish owner, it’s important to keep an eye on your molly fish’s health. Here are some signs that your molly fish may be sick:

  1. Loss of appetite: If your molly fish is not eating or showing interest in food, it could be a sign of illness.
  2. Erratic swimming: If your molly fish is swimming erratically or struggling to maintain balance, it could be a sign of swim bladder disease or other health issues.
  3. Discolored or cloudy eyes: If your molly fish’s eyes are cloudy or discolored, it could be a sign of an infection or other health issue.
  4. Abnormal behavior: If your molly fish is hiding, not swimming around, or acting strangely, it could be a sign of illness.

If you notice any of these signs, it’s important to take action quickly to prevent the illness from spreading to other fish in the tank. I once had a molly fish that stopped eating and became very lethargic.

I immediately isolated it and treated it with medication, and thankfully it made a full recovery.

Remember, prevention is key when it comes to keeping your molly fish healthy.

Make sure to maintain a clean tank, provide a balanced diet, and regularly monitor the health of your fish.

Tank Mates

Compatible FishIncompatible Fish

If you’re planning on keeping Molly fish, it’s important to consider their tank mates. Molly fish are generally peaceful and social, and they can be kept with a variety of other fish species.

However, there are some fish that are not compatible with Molly fish due to differences in temperament or water requirements.

Personally, I’ve had success keeping Molly fish with guppies, platies, and swordtails. These fish are all livebearers like Molly fish, and they have similar water requirements.

They also tend to be peaceful and active, which makes for an interesting and dynamic aquarium.

Other fish that can be good tank mates for Molly fish include tetras, rasboras, and corydoras catfish.

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These fish are all small and peaceful, and they can help to create a vibrant and diverse community in your aquarium.

It’s important to avoid keeping aggressive or territorial fish with Molly fish. Species like cichlids or bettas may see Molly fish as competition and may become aggressive towards them.

Additionally, it’s important to avoid keeping fish with vastly different water requirements, as this can lead to stress and illness for your fish.

Overall, when selecting tank mates for your Molly fish, it’s important to consider their temperament and water requirements.

By choosing compatible fish species, you can create a thriving and harmonious community in your aquarium.

Breeding Molly Fish

Breeding MethodDescription
LivebearingMolly fish give birth to live young
Breeding TankA separate tank is used for breeding
Fry CareFry are separated from adults and fed small amounts of food frequently

Breeding Molly Fish can be a fun and rewarding experience for fish enthusiasts.

However, it is important to understand the process and requirements for successful breeding. In this section, we will discuss the mating process and fry care.


Molly Fish are livebearers, which means that they give birth to live young instead of laying eggs. To breed Molly Fish, you will need a male and female fish.

The male fish will have a gonopodium, which is a modified anal fin used for mating. The female fish will have a gravid spot, which is a dark spot near the anal fin that indicates she is ready to breed.

To encourage breeding, you should provide a well-maintained aquarium with plenty of hiding places and plants.

You can also adjust the water temperature to around 78-82 degrees Fahrenheit and maintain a pH level of 7.0-7.8.

Once the male and female fish are ready to breed, the male will chase the female around the tank and attempt to mate with her using his gonopodium.

Fry Care

After mating, the female Molly Fish will give birth to live young within a few weeks. The fry will be small and vulnerable, so it is important to provide proper care.

You can separate the fry from the adult fish using a breeding trap or a separate tank. The fry should be fed small amounts of food several times a day, such as crushed flakes or baby brine shrimp.

You should also maintain a clean and well-aerated aquarium with a temperature of around 75-80 degrees Fahrenheit.

As the fry grow, you can gradually increase the amount and size of their food. I have personally bred Molly Fish in the past and found it to be a rewarding experience.

It is important to be patient and provide proper care for the fish during the breeding and fry care process. By following these guidelines, you can successfully breed and raise healthy Molly Fish.

Recommended Products:

  1. Aqueon Aquarium Fish Tank Starter Kit – This kit includes a 20-gallon tank, LED lighting, a hang-on-back filter, and a heater, making it a great choice for setting up a tank for molly fish.
  2. Tetra Whisper Air Pump – This air pump is a reliable and affordable option for providing aeration to your molly fish tank.
  3. Seachem Flourish Tabs – These plant fertilizer tablets provide essential nutrients to live plants in your molly fish tank.
  4. API Aquarium Water Test Kit – This kit allows you to monitor the pH, ammonia, nitrite, and nitrate levels in your molly fish tank, helping you maintain good water quality.
  5. Omega One Flake Food – This high-quality flake food is a great choice for feeding your molly fish a balanced diet.
  6. Python No Spill Clean and Fill Aquarium Maintenance System – This handy tool makes water changes and tank cleaning a breeze, helping you maintain a healthy environment for your molly fish.
  7. CaribSea Eco-Complete Planted Aquarium Substrate – This substrate is specifically designed for planted aquariums and provides essential nutrients to live plants in your molly fish tank.
  8. Hikari Freeze Dried Bloodworms – These freeze-dried bloodworms are a great source of protein for your molly fish.
  9. Marina Floating Thermometer – This thermometer helps you monitor the water temperature in your molly fish tank, ensuring that it stays within the recommended range.
  10. API Stress Coat Water Conditioner – This water conditioner not only removes chlorine and other harmful chemicals from tap water, but also contains aloe vera to help reduce fish stress and promote healing.


After researching and writing this guide on Molly fish care, I have come to appreciate these little fish even more. They are a great addition to any aquarium and can bring a lot of joy to their owners.

One of the most important things to remember when caring for Molly fish is to keep the water clean and well-maintained. This can be achieved through regular water changes, proper filtration, and testing the water regularly.

Another key aspect of Molly fish care is providing a balanced and varied diet. These fish are omnivorous and enjoy a mix of both plant and animal-based foods. It’s important to feed them a high-quality diet to ensure they stay healthy and active.

Finally, it’s important to note that Molly fish are social creatures and thrive in groups. Providing them with plenty of space, hiding spots, and companionship will help them live a happy and healthy life.

Personally, I have kept Molly fish for several years and have found them to be delightful pets. Their vibrant colors and playful personalities make them a joy to watch.

With the right care and attention, they can live for several years and provide their owners with endless entertainment.


Here are some frequently asked questions about caring for Molly fish:

Q: Can I keep Molly fish with other fish?

A: Yes, Molly fish are generally peaceful and can coexist with other community fish such as tetras, guppies, and platies. However, it’s important to avoid keeping them with aggressive or larger fish that might bully or harm them.

Q: How often should I feed my Molly fish?

A: It’s recommended to feed your Molly fish small amounts of food 2-3 times a day. Overfeeding can lead to health problems and water quality issues, so it’s important to monitor their feeding habits and adjust accordingly.

Q: Do Molly fish need a heater?

A: Yes, Molly fish are tropical fish and require a consistent water temperature of around 75-82°F. A heater is necessary to maintain this temperature, especially in cooler environments or during winter months.

Q: How often should I change the water in my Molly fish tank?

A: It’s recommended to do partial water changes of 25% every 1-2 weeks to maintain good water quality. However, the frequency and amount of water changes may vary depending on the size of the tank, the number of fish, and the filtration system.

Personal Anecdote: I remember when I first got my Molly fish, I was worried about their compatibility with my other fish. But after doing some research and observing their behavior, I found that they were great additions to my community tank. I also learned the importance of maintaining a consistent water temperature and doing regular water changes to keep them healthy and happy.

Reference: Wikipedia.


Hi there! My name is Jacob, and I'm the founder of this Pet people blog that talks all about aquarium and fishkeeping. I've been passionate about fish and aquatic life since I was a kid, and I've spent countless hours learning about different species, their habitats, and how to create the perfect environment for them to thrive in.

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