Why Does My Betta Fish Have a Big Belly?

Why Does My Betta Fish Have a Big Belly?

Betta fish can get sick like any other animal, but if you walk in and see the belly of your fish is massive, what does this mean? Is it deadly?

If your fish has an extremely swollen belly, it is likely constipated. However, if the fish is female, it is possible that it is egg bound instead of constipated. There are also a few other issues that can result in bloated betta.

In this article, we will cover constipation, common causes, treatment, egg bound bettas, treatment for egg bound bettas, common causes of egg binding, tumors, and dropsy.


If your betta has a swollen area only at its stomach and it is male, you’ve got a constipated betta. Constipation is a very common condition in bettas, and unless the betta has become impacted, it is very easy to treat.

Just like people, animals can become constipated. Unlike most other animals, fish cannot become constipated from drinking too little water, only from a poor diet or very slow metabolism. Both of these are easy to correct and fix

However, impaction is different, but luckily very rare when it comes to bettas. They become impacted by eating something they cannot digest, such as a small piece of gravel or part of a decoration.

This becomes lodged in their intestines and prevents waste from being passed. Unfortunately, there is not much that you can do for this condition. Surgery is impossible on such a small animal, and it is not likely that the fish will be able to pass the blockage.

Even if the fish does manage to pass it, it could easily lead to internal bleeding and/or prolapse. A prolapse occurs when part of the intestines exits the body and hangs out of the body. This condition is another one that is difficult to treat, but the best way to do so is to stop feeding until the body can pull the intestines back inside.

Common Causes

Treatment for constipation starts by addressing what you are feeding your fish, how often you are feeding your fish, and the temperature of the fish tank. Within these three things, you will probably find the cause of your betta’s constipation.

Betta fish should only eat an amount of food the size of their eye twice a day. Their stomachs are roughly the size of their eye, and overfeeding can lead to excess waste which the body isn’t always able to process.

In terms of the type of food they eat, betta fish are carnivorous and need to eat food specifically for them. If you are feeding your betta plant-based food or food with excess fillers, it will be unable to digest this.

The best betta food is based around insects and insect larvae instead of fish. Fish based food is still acceptable, but insect-based food is closer to the natural diet of betta. If the food is based around spirulina or other types of algae, it’s a no-no.

Temperature is the final piece to this puzzle. Since fish (at least, most fish) are cold blooded animals, the environment controls their metabolism and other bodily functions. This means if their temperature is too cold, they will not be able to process as much food as they should, which can lead to constipation.

Since they are unable to process their food quickly, their digestive tract moves slowly and can easily stall, resulting in constipation. Betta fish must live in water between 78 and 82 degrees in order to keep their bodies working properly.


If the constipation is caused by either overfeeding, feeding an improper diet, or keeping your betta at the wrong temperature, you will need to adjust this. However, simply adjusting this will not work, and you need to treat them for their current condition.

The treatment is very simple and has a very high success rate. It is uncommon, though unfortunately not impossible, to lose a fish due purely to constipation.

You first need to fast the fish for three days and not feed it any food whatsoever. If the temperature was incorrect, fix this issue during this time.

After fasting your betta for three days, the best thing to do is to feed some frozen daphnia. Daphnia is a type of small crustacean that is high in protein, but also work as a laxative for bettas. If you are unable to get frozen daphnia, a blanched and deshelled pea can also work.

Only feed a small portion of these foods on the first day, twice. Feed slightly less than you normally would, as the body is not used to eating much after three days of starvation.

Your betta should be showing some improvement at this point, but if it is not yet 100% better, feed either daphnia the next day as well. If you are feeding parts of peas instead, feed some pea in the morning and normal protein filled betta food in the evening. Since too much plant matter can make things worse, you don’t want to overdo it.

Egg Bound Betta

If your swollen betta is female, she may not be constipated, but may instead be egg bound. This means that she is holding too many eggs at once and the stomach often looks like an upside-down heart.

There are several reasons that the betta may be holding eggs, but she does not always do so intentionally. Part of the treatment is similar to constipation treatment, but other parts are very different.

This condition is also easy to treat and has a high success rate. However, it is more likely to cause death than constipation, but it is still an unusual occurrence.


There are several treatment options, the easiest of which is to simply fast the female for three days. She should absorb the eggs and use those as nutrition, so there is no chance of her starving.

If this fails to work, you can try to show her a picture of male betta or a mirror. This may trigger her to release her eggs if she thinks she is about to spawn or if she needs to lose weight to escape a threat.

In addition, if you have a male betta, try showing the male to the female, but keep them separated. The females are not always able to spawn in this condition, which can anger the male and cause him to attack.

Common Causes

If betta becomes egg bound, it tends to be a random occurrence instead of something with definitive causes. However, if you are keeping a male and a female in the same tank, even if it is divided, this will cause her to hold her eggs.

You should never keep bettas together unless the tank is massive and heavily planted and there are at least five or seven. If you are keeping multiple females and one or more males, the tank must be at least 75 or 100 gallons.

If they are in a divided tank, they are aware of the other’s presence through hormones. Males and females cannot be kept in divided tanks because the male hormones in the water will constantly cause the female to hold eggs, meaning she will be egg bound constantly. This is a serious health risk and if it keeps up, she will die.


It is possible for bettas to get internal tumors, but these are normally benign, and the betta can outlive them. There are currently no treatments that exist for betta tumors.

Identifying an internal tumor in betta is essentially impossible and incredibly rare. Tumors are lopsided and asymmetrical, so there would have to be a rumpled bulge on one side of the betta that either did not exist on the other or was significantly smaller and of a different shape.


Dropsy is another issue that can cause a betta to swell. The swelling will extend past the belly area and will occur all over the betta. This is accompanied by scales sticking out to the side, giving a pine cone appearance from the top, because the scales themselves swell and bulge outwards.

Dropsy is a symptom of kidney failure because a fish’s kidney filters excess fluid outside of the body, but once it fails, that fluid fills up the body. The survival rate of dropsy is in the single digits, and most opt to humanely euthanize a fish with dropsy.

The best way to treat the fish is to use Kanaplex as instructed and add 1 tbsp. of unscented Epsom salt per 5 gallons of water to the main tank. Epsom salt can help draw excess fluid out of the water and can be used as part of constipation treatment, but it is normally unnecessary.

In conclusion, if your betta’s belly is swollen, it is likely either constipated or egg bound. Both conditions have high survival rates and are easily treatable. If the swelling is largely uneven or covers the whole body, it is not one of these conditions and is much more difficult to treat.

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