Why Is My Molly Fish Bloated? 7 possible causes

Why Is My Molly Fish Bloated

Bloating in fish is one thing almost every aquarist has faced at one time or the other. There are many reasons this could happen, and we will discuss all of them in this article. Molly fish are hardy freshwater fish, they are colorful and active, that’s one of the reasons many aquarium hobbyists like them, but they are not without problems too. Just like other fish, they could bloat too.

I quite understand how frustrating and sad it could be seeing your fish get unnecessary fat, and if that is what you are passing through or passed through and you want to know why it happened and how to prevent or treat it, then read this article to the end to understand everything.

Why is my Molly fish bloated? Molly fish could become bloated as a result of Dropsy disease, Overfeeding, Constipation, and pregnancy.

Why Is My Molly Fish Bloated

Mollies are very lively fish, if they suddenly start getting fat, then there must be something wrong, which we will discuss In a minute.

The issue of fish getting bloated is a general issue, which many people have suffered from, including professional or experienced fish keepers because it could happen all of a sudden without you knowing, thereby getting you unawares unless you are practising some acts that will prevent such from ever happening.

So, if yours is bloated, then here are the possible reasons for that.

Why Is My Molly Fish Bloated?

If you are a victim of this, and you may be wondering why then here are the reasons:

1. Pregnancy: Pregnancy is one of the reasons why your Molly fish could become bloated all of a sudden.

Mollies are livebearing fish, which means, they don’t lay eggs, when they get pregnant, they carry their babies in their stomachs and deliver them when they are ready or when they mature.

Being livebearing fish means that once they become pregnant and the babies form in their stomach, it will enlarge them, and make them bloat all of a sudden, especially on the stomach side.

Although many other things could make your Molly fish and other aquarium fish bloat, to be sure it is pregnancy, check the gravid spot, and if it is bloated, that’s a good sign of pregnancy, or if the fish is somewhat transparent, you might even see the black eyes of the babies in her stomach.

Mollies are not asexual nor hermaphrodites, but they could store male sperm in their body and use it to fertilize their sex organs to become pregnant.

So, they could become pregnant even without the presence of a male, so hoping to see a male around to determine if she is pregnant or not is not a good idea.

Just check these signs above, and if you are sure the fish is not pregnant, then, move down to other factors that may cause bloating.

2. Constipation: Another reason why your Molly fish is bloated may be as a result of being constipated.

This happens as a result of the stomach, or esophagus getting blocked by something, which could be undigested foods, diseases, etc.

When this happens, the fish will no longer be able to digest the foods it ate, and those foods will stay undigested in the body, thereby making the body bloat.

When this happens, the fish will no longer be able to poop, which is a way to remove those undigested foods, and even when they do, the poop will be thick and hard and might be very tiny too.

Many foods could cause this, especially bad fish flakes and some bigger foods, and also cold temperature too, making the Molly fish unable to digest its foods at such temperature.

So get a heater and put the temperature normal first, then stop feeding the fish for 3-4 days, and when they are almost starving, feed them with foods like pea and other vegetables that they could easily digest and as time goes, continue feeding them like before, but with healthy foods this time.

3. Overfeeding: Your Molly may be bloated because it is eating a lot of food.

Many fish, including Mollies, are pigs when it comes to food, meaning that they could eat a lot of things and continuously too.

Fish doesn’t have any limit when it comes to food, they will eat and continue eating, for the fact they have unlimited access to food.

Giving them food repeatedly could cause Overfeeding, which could cause them to bloat.

Overfeeding will make them poop a lot, which will in return dirty the water, and breed ammonia and nitrite, and many other bad chemicals, which will make them sick and maybe bloat, and also make them fragile by weakening their immune system.

So the normal rate you should feed them is twice a day, and with the quantity, they could finish in maybe 5-10 minutes.

4. Your fish may have swallowed something, and it is blocking its throat or stomach.

We all know that fish are scavengers and would eat anything, especially when they are hungry.

There is every chance that it has swallowed, maybe a small stone, and it is unable to digest, thereby blocking the body from digesting other foods, and causing it to bloat.

When this happens, the best idea is to get a specialist ( Vet ) to look into the issue and know how best to go about it.

5. Dropsy disease: Dropsy is a very bad and fatal disease for many aquatic animals, which fish is among.

This disease will damage all the internal organs by bloating them with fluid ( water) thereby making the animal involved to die a slow, but painful death.

All aquarists fear this disease because, once it has touched the organs, the animal won’t remain as healthy as before, even if it is cured, and the animal will die before its lifespan elapses.

There are few methods that people use to cure animals suffering from this, they are, putting the sick fish or animal in a bowel with 2 gallons of water and 1 spoon of aquarium salt.

They do this to relieve the animal, but it doesn’t cure them.

Another method is to insert a small needle carefully into the animal, making them be relieved.

Disclaimer – I don’t support any of these, and I don’t give medical advice, so the best idea is to get a Veterinarian doctor to handle the case, in order not to hurt your fish the more.

6. Obesity: Sometimes this could happen out of fatness or obesity.

Fish can fatten themselves up to endure a long period of scarcity of food.

They do this more in the wild than in captivity, because they normally eat in captivity, unlike in the wild where they eat when they are lucky to see any food.

So, if you stop feeding them, for a while, they could get fat, as a way of protecting themselves from the imminent death which comes with starvation.

So, they could fatten themselves up, and if yours isn’t being fed, or you traveled, then this is very likely to happen.

7. Poor Water Quality/ Tank: Another thing that could cause this in fish is bad water and tank.

No animal can thrive in dirty water full of diseases and in a tank that did not cycle fully, etc.

Molly fish are tropical and freshwater fish, so they could only thrive in a water temperature of 68-80°F and a pH of 8.2.

So, when they are not in their ideal tank and water condition, their immune system will be weak, and they may be easily infected by the slightest diseases around.

How Do I Know If My Molly Fish Is Fat Or Pregnant?

Sometimes you couldn’t able to easily detect if your Mollies are pregnant or bloated, so you might think they are bloated, but to be sure they ain’t, here are the tips to check them.

When the gravid spot is bloated, the fish is very likely to be pregnant. Again you might even see the eyes of the babies if the Molly fish is transparent enough.

Another way to find out is, if the fish becomes very aggressive and territorial, and will go to the bottom always, then, she is pregnant and wants to give birth.

These are the easiest signs to look out for, to be sure your Molly fish is pregnant or just bloated for other reasons which I explained above.

When you find out, the next thing to do is to get her into a breeding box to avoid others stressing her or her harming others too, and to keep the fry safe too.

Why Does My Fish Have A Fat Belly?

If your fish have a fat belly, there are two main reasons for that. It’s either it is pregnant, or it is a result of overfeeding.

As I explained above, fish don’t know their limit when it comes to food, so, they will eat as long as there is food, and that’s why they could easily Overfeed, which could sometimes cause problems for them.


These are the reasons why your Molly fish is bloated, so treat them accordingly and get a veterinarian doctor if things get complicated for you. And I don’t in any way advise self-medication.