Why Do Mollies Die After Giving Birth? 8 Reasons and Their Solutions

It’s difficult to accept when your molly dies after giving birth. Pregnant mollies experience stressful situations that require extra care and a nutritious diet. Therefore, after providing all these then your wet pet dies after birth, the first question you’ll have is, “Why do mollies die after giving birth?”

Normally, mollies die after giving birth due to stress, unfavorable environment, postpartum health issues, cannibalism, general body weakness, and malnutrition. You can prevent such deaths by proper feeding, providing a suitable environment, and monitoring tank parameters regularly.

In this article, I’ll discuss the main reasons why mollies die after giving birth. You’ll know where these issues emanate and how to prevent them for your fish’s well-being. Keep reading!

Why Do Mollies Die After Giving Birth? 8 Reasons and Their Solutions

Your molly fish dying just after giving birth is a challenging situation. You may start blaming yourself for not providing the best care for your fish. However, the main reasons why mollies die after giving birth include:

1. Severe Molly Fish Stress

Why do mollies die after giving birth

Generally, giving birth is a stressful process for mollies. Because birthing is a procedure that involves physical strain, your fish may get extremely anxious and stressed, affecting its immunity.

Consequently, the molly may not feel safe and ready to drop the fry even though they’re due. At this point, birth complications such as dystocia may arise.

Stress at birth can be exacerbated by the following:

  • Predation
  • Bullying from other fish
  • An overcrowded space
  • Lack of ideal hiding spots
  • Poor water quality
  • Poor diet and malnutrition

A stressed molly fish has a weakened immunity, the primary reason for potential death. 

It’s imperative to note that low immunity in molly fish makes it vulnerable to disease-causing pathogens like bacteria, viruses, fungi, and parasites.

Moreover, stress lowers the fish’s appetite, which could impact its nutrition. The outcome is starvation and, if unmanaged, death.

Fish parents should also watch out for stress, as it may lead to organ dysfunction in pregnant molly fish. The fish dies if any organ fails during birth, including the heart, kidney, or liver.

Also Read: Black Molly Pregnancy Stages and How to Prepare for Delivery


Ensure your fish doesn’t encounter extreme stress factors. For example, when female mollies are about to give birth, transfer them to a special hospital or breeding tank where there’s no distraction, mess, or pressure from other fish.

Provide a rich diet that supplies all essential nutrients a pregnant molly needs. The best diet consists of protein-rich foods such as brine shrimp or bloodworms. These are vital for fry development, especially when supplemented with fresh or frozen vegetables. 

A molly fish’s nutrition is crucial for a healthy pregnancy and safe birthing.

2. Poor Water Quality

When water parameters are not within the appropriate range, your molly fish can suffer to death, especially when giving birth. For instance, ammonia and nitrite can choke the fish even when present in small traces.

Similarly, high nitrates can also trigger excessive algae growth. Excessive algae congests the tank and even consumes the oxygen meant for fish.

As for the pH, molly fish suffer in acidic conditions denoted by pH values below 7. Therefore, extreme acidity can burn the fish’s skin and cause them great distress.

What about water hardness? 

Molly fish are unlikely to enjoy staying in soft water. If you’ve not monitored water hardness recently, your fish could be in danger of lacking magnesium and calcium – two vital elements mollies need for proper development. Remember, they’re hard water species.

Usually, poor water quality is a result of the listed impurities. If left unmanaged, the water becomes deoxygenated, affecting and even killing the vulnerable molly fish giving birth.

Find Out: Why Is My Molly So Fat? 4 Main Reasons and Their Remedies


Managing the water quality is the best way out of this problem. 

To that effect, monitor the water parameter levels regularly. You can use a high-quality aquarium kit to test the parameters.

Here is a quick table summarizing the correct ranges per parameter.

Water ParameterAcceptable Range
Ammonia0.0 ppm
Nitrites0.0 ppm
Temperature72-82℉ (22.22-27.78℃)
Nitrates<50 ppm
General hardness12-20 GH
Alkalinity10-18 KH
Optimum tank parameters for molly fish survival

You must amend these conditions regularly, depending on the aquarium kit results. Usually, you would need to add aquarium salt, conditioners, and additives to keep the parameters in check.  

3. Birth Complications

Altogether, giving birth is a laborious process

Your molly fish requires a lot of energy during birth to deliver the fry safely. The fish may experience birthing complications if it has a lower immunity.

Difficult or obstructed labor, also called dystocia, can occur if the molly has its fry positioned awkwardly in the belly. So, she may struggle to expel them. If this occurs, it can lead to distress and potentially fatal health issues.


Ensure the fish is in top health during pregnancy. 

For instance, observe a healthy feeding program – providing your fish with enough protein foods such as live or frozen brine shrimp and bloodworms. 

Remember to add blanched veggies like lettuce in the diet to boost immunity.

In addition, birth complications would not affect your mollies if you provided a quiet place for delivery

A separate breeding tank is a good starting point. Yet, keep aggressors away from that tank or provide enough hiding points.

Subsequently, your fish will develop a solid immunity, all thanks to proper nutrition and a suitable environment.

4. Giving Birth Frequently

Pregnant molly fish

Generally, mollies have a 28-day gestation period

A serious mistake most aquarists make is breeding their mollies in close succession. Doing this drains the fish completely because they use a lot of energy.

Ultimately, your fish may become weak, get infected with other conditions, and eventually die. The bottom line is that mollies’ lifespan is shortened when they breed frequently without sufficient recovery time.


Set up separate tanks for males and females to prevent breeding. This is a direct method that eliminates accidental mating in molly fish.

Moreover, you can reduce the male-female ratio in the tank. Have one male amidst three female mollies.

You can use more tank decorations to create extra hiding spots for your fish. These hiding areas will be vital when males begin chasing after females.

5. Infections

Survival at birth is compromised when mollies gets infected with certain disease-causing organisms like bacteria or parasites. 

Diseases like fin rot or dropsy makes it hard for mollies to deliver safely, given the physical strain they encounter at birth.

One of the most common symptoms many diseases and conditions show is lethargy. A pregnant molly with fin rot may not give birth but lie on the tank’s floor looking tired. 

Even if the fish finally gives birth, postpartum health issues will weaken her, exposing her to potential death.


Treat diseases early to avoid surprise deaths. 

Ultimately, maintain the aquarium regularly – ensure the water parameters are within the recommended range as indicated earlier.

Add one teaspoon of aquarium salt like Epsom to five gallons of water to resolve swellings due to injuries. 

Alternatively, you can use broad-spectrum antibiotics to treat an advanced bacterial infection such as dropsy.

6. Aggression by Other Fish in the Tank

Aggressive behavior may erupt if you don’t separate pregnant molly fish from other members. Sooner or later, your pregnant molly sustains injuries, making her highly susceptible to brith strains.

If untreated, infections can take advantage to invade the injured tissues. You can be guaranteed that your fish wouldn’t have the energy to push out fry with an infection. Consequently, the fish may die trying to deliver her babies.


Keep male mollies and bullies in a separate tank to avoid direct contact with pregnant females. Additionally, add a bit of decoration to increase the hiding spots.

Having females in separate tanks makes monitoring the fish’s pregnancy easy and effective. This way, you can provide the best conditions for your fish during pregnancy and delivery.

7. Poor Diet

Did you know that a poor diet can cause death in pregnant mollies? 

Your fish’s diet must supply all essential nutrients the fish needs for a safe delivery. These nutrients include vitamins, proteins, and calcium.

Generally, a fish suffering from malnutrition can’t resist diseases. This is because its immunity is distressed, hence easily overpowered by pathogens.


Make sure your fish gets a balanced diet that supplies nutrients in the correct proportions. 

Feed the fish a mix of flakes and frozen bloodworms, brine shrimp, and daphnia. Vegetables such as blanched zucchini and lettuce should also be provided.

8. Low Oxygen Levels in the Aquarium

After delivering, the mother molly is usually weak and needs more oxygen. However, some aquariums have less oxygen due to high impurities. 

Thus, the fish suffers respiratory distress in such environments. This can harm both the mother molly and its younglings causing mortalities.


Use a high-quality water filtration system to remove impurities from the aquarium. Always check if the filter is working to avoid last-minute calls. Filtration systems purifies the water, making it fresh and clean.

Furthermore, change the water regularly to ensure you don’t have a misbalance in the water parameters every other time. Perform a 25% water change every two weeks for the fish’s well-being.  

What to Do When a Molly Fish Gives Birth

When a molly fish gives birth, the mother should be returned to the main tank immediately. Otherwise, she might eat all her fry if left in the breeding tank for a short while. This is because mollies lack parental care. 

Even so, some aquarists intentionally leave mothers with their fry to reduce the youngling population to what they can effectively manage. 

That said, the fry should be cared for right from birth. Feed them a balanced diet of baby brine shrimp, tiny worms, and ground flakes for easy ingestion. 

Have a feeding program that guides you to feed the fry. Food should be given in small amounts – like a pinch at ago – multiple times daily.

You also want to incorporate extra floating plants in the tank. These plants enhance shelter and hiding spots in case large fish are present in the tank.

Don’t forget to change water regularly to drain off impurities. 

Finally, give the mother molly enough food and proper care to help her recover from birth strains. 

Can Molly Fish Live With Their Babies?

Dalmatian molly fish

Molly fish can live with their babies only after they’ve grown into fingerlings and are big. However, fry are usually eaten when left with their mother in the same tank. Mother mollies see their little ones as prey, and since they lack parental care, they hunt after them for food.

At some point, you may transfer fingerlings that have grown large enough to escape predators to the main tank. When they are big, it’s easy for them to sense danger and hide from other fish and their mothers. 

Even better, big fish cannot swallow them, given their increased size. Thus, the little mollies can’t practically fit in the big fish’s mouth. 

When you mix molly mothers and their older fry, ensure you provide a large tank to accommodate all of them, improve hiding spots, maintain excellent water quality, and provide enough high-quality feed for a comfortable environment. 

Why Are My Baby Mollies Dying? 

Your baby mollies are dying for the following reasons:

  • The outbreak of diseases and parasites like dropsy, fin rot, and popeye in the tank
  • Poor tank conditions such as increased impurities, inadequate oxygen, algae overgrowth, overcrowding, and unchanged water
  • Inadequate nutrition due to insufficient feeding, wrong feeding schedules, and low-quality feeds
  • Genetic defects such as deformed spines due to inbreeding 
  • Some molly babies die of predation by large fish, including their mothers

For these reasons, raising an entire shoal of baby mollies is hard without losing some. However, experienced aquarists can still successfully raise most of the fry. 

8 Ways to Keep Mollies from Dying After Giving Birth

The following tips should help you keep mollies from dying after giving birth:

1. Provide Adequate High-Quality Feed

To improve your molly fish’s nutrition, ensure you give them high-quality feed rich in protein and minerals. For instance, provide frozen or live bloodworms, black worms, daphnia, and brine shrimp.

Vegetables such as zucchini or squash should be chopped and given to the fish for a boosted immunity. Remember, your molly mother needs to recover as fast as possible.

2. Help Your Molly to Take a Break From Breeding

Most importantly, help the fish take a break from further breeding activities. Mollies need only 28 days to carry and deliver fry.

You can separate females from males to prevent subsequent mating.

3. Provide a Spacious Tank

An overcrowded tank can lead to molly fish death right after delivery. This is due to excessive pressure from other fish, especially males chasing them for personal reasons.

That said, you can buy a larger tank. Having enough space allows your new molly mother to enjoy adequate space to rest, hide, and even roam without being bothered.

4. Change Water Regularly

The birth process weakens and drains your molly fish significantly. Hence, the need to provide a favorable environment – beginning with a water change.

Ideally, perform a 25% water change after every two weeks. This keeps the water fresh and clean, maintaining water parameters at the required levels.

5. Maintain Correct Water Chemistry

Additionally, keep the water chemistry at ideal levels. Ensure the water has no ammonia and nitrites, as these are toxic to fish.

Maintain nitrates at less than 50% ppm while keeping a pH of 7-8, a general hardness of 12-20 GH, and a 72-82℉ (22.22-27.78℃) temperature range.

6. Urgent Treatment of the Infected Fish

Urgently seek veterinary support if you notice a sick fish. Your vet will recommend antibiotics for most bacterial infections, depending on the situation.

Similarly, adding Epsom salt to water can help assuage wounds on the fish’s skin.

7. Use an Efficient Filtration System

Filters are vital in aquariums as they remove impurities in the water, keeping it clean and fresh. In that regard, ensure you have installed a high-quality filter to help expel excess toxins that result from food remains and fish wastes.

8. Keep a Close Eye on Your Fish

If the timing is incorrect, you may do all other things and still lose your fish. Thus, tracking the fish’s progress after delivery is hugely important.

Make sure that no day passes without checking on the fish. Regular monitoring helps you discover any telltale signs like erratic behavior or physical disease symptoms.

Final Thoughts

The question, “Why do mollies die after giving birth?” is intriguing.

Most aquarists want to know what causes this mysterious phenomenon and how to prevent it. With the points shared in this article, I hope you’re well-equipped with the knowledge to ensure the well-being of your molly after giving birth.

A rule of thumb is to maintain optimum water parameters and prevent overcrowding.

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