How Do You Know When A Molly Will Give Birth? (5 Quick Signs)

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Breeding fish is one of the most exciting things in fishkeeping. However, I usually find it pretty challenging to pinpoint the exact moment in which I should act. For example, when I tried to breed mollies, I didn’t know how to tell when a pregnant molly fish was about to give birth. To get a better understanding of this, I started researching the topic quite profoundly.

Pregnant mollies that are about to give birth are usually presented with a squared, distended stomach. At this point, the gravid spot will become opaque and relatively darker. Also, mollies close to delivery tend to shiver, lose their appetite, and hide behind objects such as plants and decorations.

As we move forward, I will take you step-by-step through what you should do if your pregnant molly fish is close to delivery. I will also explain how long it takes for mollies to give birth and what could potentially delay it.

Also Read: Pregnant Molly Fish 101

How Can I Tell If My Molly Is About To Give Birth?

Female mollies are usually ready to reproduce at six months of age. Female mollies breed by copulating with male mollies. Because they are livebearers, their eggs are fertilized from inside their bodies, with the female mollies eventually giving birth to live fish.[1]

It is challenging to pinpoint the exact moment that a female molly will give birth, especially since you have no way of knowing when it copulated with a male fish. However, you can look for sure signs that will either manifest or grow more prominent as your molly’s pregnancy advances. They include:

1. Squared Stomach

Pregnant mollies always develop swollen bellies. However, on its own, this development won’t tell you anything. But as a molly’s pregnancy advances, if you continue to observe the molly, you will notice that the belly is growing larger and changing shape, to an extent.

As the molly approaches its due date, its distended stomach will develop a square outline.[2] Once this happens, you can conclude that the molly is close to giving birth. Professional aquarists will encourage you to look for a v-shape at the bottom.

2. Opaque Gravid Spot

Anyone who has ever owned Livebearers knows about the gravid spot. They understand that it is found near the anal tail and that it appears during pregnancy. However, they might not realize that the gravid spot keeps changing throughout the pregnancy, becoming darker and darker. 

You can use the appearance of the gravid spot to chart the molly’s pregnancy. You may even take photos each day and check for changes in coloration. Once the gravid spot becomes opaque and you can no longer see through it, your molly is probably about it give birth. 

In some cases, you may even see the eyes of the fry through the thin walls of the gravid spot.[3] At the early stages, the gravid spot merely resembles a dark triangle. However, as the molly is ready to give birth, you may notice eye movements in this area.

3. Timid Behavior

Pregnant mollies have been known to develop aggressive tendencies. But in many cases, this attribute is only displayed against fish that trespass upon the molly’s territory. Most of the time, the pregnant molly prefers to stay out of sight.

It will become even more reclusive as its due date approaches.[4] It will seek out the dark sections of the tank in the hopes of identifying a safe and peaceful environment within which it can give birth.

That is why aquarists are encouraged to provide pregnant mollies sufficient cover in the form of plants and decorations. The absence of hiding places creates a sense of insecurity and discomfort among pregnant mollies. 

That can introduce complications since pregnant mollies are quite sluggish and lethargic. Since they are far less mobile, they need the protection that plants and decorations offer. A pregnant molly that spends most of its time in hiding is close to giving birth.

Also Read: Why Is My Pregnant Molly Hiding?

4. Less Interest In Food

Pregnant Mollies don’t eat as much as their non-pregnant counterparts. Some mollies will cut back on the quantities they consume. Others will stop eating. They will ignore the food you add to their tank, a development that tends to panic some aquarists that know mollies as enthusiastic eaters with large appetites.

Every aquarist understands the importance of providing their fish with a balanced diet. That is the only way to keep them healthy and stress-free. However, your pregnant molly’s loss of appetite shouldn’t worry you. It is entirely typical, and a sign that the creature is almost ready to give birth.

5. Shudders & Shivering

Pregnant mollies that are about to give birth will begin to swim differently. Sometimes you will see your fish shivering for brief periods. The more your pregnant molly is approaching her due take, the more frequent she will shake her tail.

The reasons for the phenomenon tend to vary and sometimes indicate that your fish is stressed. For example, in fish that are not pregnant, that could signify that the water is too acidic. You may notice this behavior in other livebearers, such as swordtails and guppies.

Do Mollies Poop A Lot Before Giving Birth?

Mollies usually poop a lot when you overfeed them. However, this behavior is also expected in pregnant mollies before giving birth. Other livebearers such as guppies have shown similar tendencies.[5] In fact, some aquarists have noticed excessive pooping in mollies that are mere hours away from giving birth.

That isn’t always the case, though. Some pregnant mollies eat food in such small quantities that they are incapable of manifesting this behavior. But if your pregnant molly is eating a healthy amount, it will poop a lot.

In such cases, you are encouraged to feed it a healthy diet that includes plenty of live foods and plant matter. You should also maintain its diet after it gives birth. The molly will need all the nutrients you can give it to regain its strength.

How Long Does It Take For A Molly To Give Birth?

Mollies can give birth roughly once every month, even in the absence of a male fish. That is because they can store sperm that can be used later on to fertilize their eggs. The duration of the birth will depend on the fish.

Most aquarists expect the process to take anywhere between one hour and twenty-four hours. However, it could just as easily take two days or even longer. Mollies are technically easy to breed. Nevertheless, they are associated with several complications, chief amongst which is that they can refuse to give birth.

Sometimes, it is a genetic issue. Some mollies are naturally built to hold fry for more extended periods than usual. In a lot of cases, though, it is an issue of external stimuli. Mollies will refuse to give birth if they conclude that their environment is unsafe.

You see this in tanks with aggressive fish. Mollies are less likely to give birth on time if their neighbors keep bullying them. The obvious solution is to place your pregnant molly in a breeding net. Unfortunately, some fish hate breeding nets.

The act of moving a molly to a breeding net could induce the sort of stress that eventually discourages the fish from giving birth on time. If bullies are not the problem, you have to consider the water conditions.

A tank with the wrong pH, temperature, and hardness will discourage a pregnant molly from releasing its fry into the world. If your pregnant molly has refused to give birth, you should take a moment to check the conditions in the tank.

To do that, I highly recommend getting the API Aquarium Test Kit (link to Amazon). That highly affordable bundle will test your water for pH, ammonia, nitrates, and nitrites within minutes. If you notice that the pH is lower than 7.5, you should perform more frequent water changes.

Mollies are not all the same. You shouldn’t expect them to act the same way or to follow the same schedule once they fall pregnant. That being said, in an ideal situation, the birthing process shouldn’t exceed 24 hours.

If you investigate your aquarium, you might be shocked to learn that the water conditions are lacking. Of course, many aquarists will also encourage you to apply some patience. Sometimes you have no reason to worry.

Even with a new tank and a healthy molly, the birthing process could exceed the expected limit. In such cases, all you can do is wait. Your molly will complete the birthing process when it is ready.

Also Read: How Long Are Molly Fish Pregnant?

What To Do With A Molly That Is About To Give Birth?

If you’ve noticed the signs above, your pregnant molly fish is likely about to give birth for numerous fry. At this point, you must take the necessary steps. They will help you to keep the fry and the pregnant molly safe from hostile environments.

Step 1: Separating the Pregnant Molly From the Main Tank

That is an essential step. Pregnant mollies show weakness, and aggressive tankmates will take advantage of it. They will probably attack your molly and chase her consistently. Therefore, you should put the pregnant molly in a separate tank.

It would help if you also kept in mind that once the molly gives birth, her fry will be prone to attacks. Putting the pregnant molly away will keep both the mother and the fry safe. Nevertheless, I suggest doing that gently.

Avoid using nets for that matter. The pregnant molly is susceptible at this stage and may get hurt or refuse to deliver if mistreated. That is why I recommend using a cup or a bowl. Place the empty container beneath the molly, and she will be forced to get inside it.

Step 2: Adjusting the Water

The water parameters within the breeding tank must be suitable for a pregnant molly. The best choice would be to move some of the water from the last tank to the new one. That will prevent the need for acclimatization.

Even if the previous tank featured relatively low water quality, setting up the perfect conditions may kill your molly. That is because the adjusting process is stressful. Some fish cannot acclimatize to a new temperature or a pH range so quickly.

However, you should make sure that the new tank features a heater and a filter. You may also use airstones for oxygenation. That will relieve the stress and will prevent the temperature from dropping. The ideal range should be 72-78 degrees F.[6]

Step 3: Introducing Plants and Decorations

From this point, successful delivery is up to your pregnant molly. However, you should introduce a few decorations and plants to the breeding tank. That is because the pregnant molly herself is dangerous for the newborns.

Even though we’ve eliminated the aggressive tankmates issue, the mother molly will happily consume her own fry once born. Mollies show no sympathy and will consume whatever fits in their mouths. Make sure that the plants are relatively low since fry usually frequent the lower sections.

Step 4: Taking Care of the Fry

Once the molly gave birth, you can move her back to the original tank. She won’t take care of the fry and will only cause stress to the newborns. Get her back to the original tank by using either a net or an empty container.

Now, you should feed the fry. You can do that by using the mother’s food, although it would be best to grind it a bit. That is because whole flakes won’t fit in the fry’s mouth properly and will sink to the bottom before it gets to chance to eat.


Mollies that are ready to deliver are usually presented with physiological changes. Those include a darkening gravid spot and a distended, squared belly. Those molly fish also tend to be shyer and frequently get behind plants and decorations.

Once you see those signs, move the pregnant molly to a breeding tank. Ensure that it is set with the right conditions and features enough hiding places for the future fry. That will prevent the mother from attacking her offsprings.