It might be confusing to see your Betta going from healthy and energetic to puffy and unenthusiastic.
In my experience, there may be multiple reasons why your Betta fish is having a bloated belly and appears to be lethargic. There’s no need to panic, however, since a swollen stomach does not always mean the worst for your aquarium pet fish.
A bloated abdomen may sometimes indicate harmless constipation, and not the fatal Dropsy or the annoying Swim Bladder Disorder.
In this article, I will explore the main causes of bloat in Betta fish.
Knowing how fish bodies work can help to prevent severe illness.
Why is your Betta fish having a bloated tummy?
Looking at your Betta’s swollen abdomen might be overwhelming.
Sometimes the condition may be accompanied by difficulties with swimming and breathing.
The most common reasons for a Betta fish to have a bloated stomach are overfeeding with nutrient-dense foods or ones that are poor in fiber, substandard water quality, bacterial infections, and internal parasites.
If those are left untreated, they may lead to a belly that looks extremely swollen, severe constipation, and conditions such as Swim Bladder Disorder, or Dropsy in the fish.
If a female Betta has a swollen belly, it may also be that she is egg bound.
All of the aforementioned conditions can be cured as long as they are properly and timely diagnosed.
1. Feeding foods that are too nutrient-dense and break down too quickly
A bloated abdomen in a Betta can often be a result of the fish eating foods that are too nutrient-dense yet disintegrate too quickly when inside the stomach. These types of foods trigger a negative response that slows the emptying of the stomach.
The function of this body reaction is to prevent the intestines of the Betta fish from getting overwhelmed with nutrients.
A prolonged triggering of this response leads to food retention in the belly of the fish and therefore bloating from severe constipation.
In some cases the stomach may become so swollen it would start appearing white on the outside.
When I was initially researching the possible causes of belly bloat in fish, I stumbled upon this one study that suggested the aforementioned scenario as a possible cause.
The study kind of opened my eyes to the type of foods I was giving my Betta.
Can you guess which foods are too nutrient-dense and get digested too quickly?
If you guessed “pellets” then you’re following.
Pellets are basically compressed flakes which are nonetheless fast dissolvers themselves.
Anyway, the pellets always come with super high protein content and are made to be easily digestible.
Betta fish are also genetically prone to bloat (same as Goldfish) and the two effects seem to stack up quickly.
The mechanism that slows the stomach emptying is called enterogastric control.
When it activates the food remains way longer in the fish’s belly.
If you feed the fish with nutrient-dense types of food for a prolonged period of time, the mechanism would lead to decreased water absorption.
It might seem that this should work against bloating, but not in this particular chain of events.
After doing some more research, I found that decreased water absorption will force the gills of the fish to start extracting more salt from the outside environment and pump it back into its body. Consequently, the increased water retention leads to excessive swelling not only in the abdomen but also throughout the whole body cavity, a symptom known as Dropsy.
The scientists in the study suggest that in such cases the fish should be fasted, and its nutrient intake reduced.
In the case of a Betta fish you’ll likely need to cut the pellets or flakes from its diet entirely.
What closely resembles the menu of a Betta in the wild would be bloodworms, daphnia, and, occasionally, Mysis or brine shrimp.
These foods have some necessary insect fiber that helps digestion, and also lack the high-fat content of flakes and pellets.
The latter are also highly processed and the protein source can often be something that’s not found throughout the natural diet of the fish.
I will recommend a feeding schedule that has worked for me and my fish when nothing else has.
To treat bloating caused by nutrient overload in Betta fish try the following:
- Day 1: Fast the fish.
- Day 2: Fast the fish.
- Day 3: Feed the Betta a tiny amount of bloodworms, once.
- Day 4: Fasting.
- Day 5: Feed the Betta a small amount of Daphnia, once.
- Day 6: Fasting.
- Day 7: Feed a small amount of Daphnia or Bloodworm, once.
Make sure to only feed the fish an amount that resembles its eye-socket in volume. On feeding days, only feed once.
Repeat this regimen until the bloating subsides completely.
To improve the Betta’s chances of success with this treatment you should also maintain pristine water quality, in order to reduce the stress on the fish.
Don’t do large water changes as these are stressful to the fish. Instead, perform smaller (no more than 10 to 15%), more frequent ones.
Something that could help with further reducing stress in fish is API’s Stress Coat Plus.
You can find that and all of the aforementioned freeze-dried live foods at most larger pet stores online such as Chewy. Here are some links for your convenience:
- Freeze-dried Bloodworms.
- Daphnia + Mysis Shrimp + Bloodworms.
- Freeze-dried Mysis shrimp.
- API Stress Coat Plus.
2. Bacterial kidney infections
A bacterial infection may be the reason behind a lethargic Betta with an extremely bloated belly. Harmful bacteria may damage the kidneys of fish, hindering their ability to regulate bodily fluids. This causes the body of a fish to absorb too much water, which leads to swelling that often starts from the stomach.
I’ve had the chance to observe a lot of sick Betta fish during my years of helping friends with their fish keeping endeavors.
Speaking from experience, a hidden bacterial infection is the most common reason for a Betta to mysteriously develop a bloated abdomen out of nowhere.
I should also note that, occasionally, a bacterial infection may develop into an abscess.
Just like the cancerous tumor, an abscess can appear anywhere on the body. When it appears on the Betta’s stomach, the abscess makes the fish look bloated on one side.
Another symptom of this type of infection is your fish swimming with its fins very close to the body.
The abscess can damage the internal organs of the Betta, leading to Swim Bladder disorders.
Anyway, it’s important to remember that bacterial infections in Betta fish are often the result of poor water conditions and stress.
However, these should be taken care of after the infection has been cured.
On that note, any type of bacterial infection in aquarium fish should be treated immediately.
If no action is taken, the whole cycle will repeat, as Betta’s immune system will be compromised and the fish will be more susceptible to future infections and diseases.
Start performing regular water changes to avoid the build-up of ammonia and use a good antibacterial medication.
My experience has been that amoxicillin is a sound choice for treating bacterial infections that cause bloating in a Betta.
When I’ve treated Betta fish this way the bloat usually subsides a couple of days after the treatment has been initiated.
Just make sure to use 100% pure Amoxicillin trihydrate.
3. A diet poor on fiber
A diet that’s low on fiber can cause severe constipation in Betta fish, which may eventually lead to bloating. The symptoms of constipation bloat in a Betta could include a swollen stomach, that almost appears white, rare or no defecating, and troubles swimming straight.
To treat a constipated Betta you need to sparingly feed it quality food that’s high on fiber followed by fasting the fish for a couple of days.
Daphnia, which is a type of water flea, can be found in fish stores and is known to provide beneficial fiber and a laxative effect for fish. Bloodworms are also an excellent source of fiber for Betta fish with constipation.
Another option here would be a blanched, deshelled pea. Feed the fish with 1/4th of the pea and skip feeding the next day or two.
I prefer feeding Daphnia or Bloodworms to a Betta fish because these foods are a natural source of fiber for it whereas the fiber in peas comes from a land-based plant.
Constipation is easily treated in fish and if that’s the reason behind the swollen belly of your Betta, you should see the bloat go away in a couple of days.
Note that you can fast the fish for 2 to 3 days without worrying, because a healthy specimen can live for up to 2 weeks without food.
There are many brands of fiber-rich foods and you can likely use any of them to feed your Betta.
4. Internal parasites
Sometimes, the belly of a Betta fish can become bloated due to internal parasites.
The most common internal parasites that may cause this are roundworms such as the Camallanus worm.
If no treatment is initiated, internal parasites can affect the swim bladder of the Betta or promote Dropsy. The first is characterized by buoyancy issues and upside-down-swimming and the latter by fluids building up in the whole body of the fish, and not just the stomach.
Other symptoms to confirm a parasitic infection in Betta fish may be:
- pale body colors
- white stringy poop
- listlessness and lethargy
- erratic movements
- lack of appetite or…
- eating normally yet losing weight.
It could be surprising to some pepople that when the Camallanus worms are fully grown, they may be seen coming out of the Betta’s tail area.
This can be a shocking view to someone, as I remember it was for me.
Anyway, you should also check for any redness in that area, and monitor the fish for erratic swimming.
It’s important to remember that some internal parasites will develop over the course of 1 to 6 months.
For this reason, most of them will go unnoticed for long periods of time.
Once you are sure that the bloating of your Betta’s belly is caused by roundworm parasites, you need to treat the whole fish tank and not just the infected fish.
Anyway, in my experience, you can treat the condition with Levamisole, which is actually a medicine for internal parasites in cattle.
I’ve seen it work excellently against parasitic bloat in aquarium fish.
On the other hand, you can get another commercial medicine if you can’t or don’t want to try Levamisole.
Praziquantel is the active ingredient you should be after.
A good product that contains Praziquantel and has proven its worth over time in the fish keeping hobby is Hikari’s PraziPro .
5. Egg Binding
If you notice a swollen abdomen in a female Betta fish and she is over 4 months old, it may be that she’s developing eggs.
If you are not sure whether her belly’s gotten big because of eggs, take a closer look and you should notice a white spot on her tummy.
In the case of egg binding, there’s nothing to worry about.
If you have a male Betta fish, you can place the couple in one tank with a divider, or you can just show the male to the female from a separate fish tank.
6. Overfeeding with large amounts of food
An overlooked reason for a Betta fish to develop an abnormally swollen stomach is overfeeding.
I remember that in my diligence to make my pet fish happy, I used to overfeed them heavily.
In my defense, I must admit that they always seemed hungry to me.
However, with time I learned that this is a common misconception.
Betta fish are opportunistic feeders in the wild and will consume as much food as they can when given the chance.
For this reason, you should not be surprised if yours looks constantly hungry.
Overfeeding on rare occasions is likely harmless to your Betta fish.
However, continuous overfeeding with dense, nutrient-rich foods such as pellets may lead to constipation, a bloated abdomen, and obesity with fat surrounding the Betta’s internal organs.
Needless to say, adding too much food to the aquarium may also overwhelm its biofilter with organic waste.
If no measures are taken, your Betta fish may end up with a belly that’s so swollen to the point that it appears white. Most importantly, your swimming buddy’s immune system would be compromised.
To avoid overfeeding, you’ll need to feed your fish no more than two times a day – in the morning and in the evening.
I personally prefer to feed my Betta only once a day.
Also, you can fast a Betta for a full day, once a week.
A Betta’s stomach is almost as big as its eye and the common agreement between hobbyists is that these fish don’t need more food volume than that.
Here’s a good regimen that will reduce the chance of a Betta developing a swollen stomach due to overfeeding:
- Switch to live or frozen live food instead of compressed, processed pellets or flakes.
- Only feed your Betta once a day.
- The volume of each meal should resemble the volume of the Betta’s eye.
- Skip a feeding day once a week.
7. Temperature Shock
A temperature shock could indirectly cause belly bloat in aquarium fish.
If the temperature becomes too low it can cause the Betta’s metabolism to slow down too much for its digestive system to work properly.
This might lead to a bloated look and internal organ damage.
To avoid this, simply raise the temperature of the aquarium water, by using a heater.
A water temperature of between 79 and 81 °F (26.1 to 27.2 °C) is ideal for most species of Betta fish.
I would like to point out that having a reliable aquarium heater really helps here. Some models can be outright garbage.
Anyway, the bloating of the stomach should subside a couple of days after the water temperature has been brought back to normal.
8. A growing tumor
In some rare cases, the stomach of a Betta fish may become bloated due to a growing tumor.
Tumors may be a result of the fish’s genetics, poor nutrition, or bad water quality in the aquarium.
The symptoms of a tumor may include a lump on one side of the Betta’s belly.
If the bloating is asymmetrical there’s a good chance that your Betta fish may be developing an internal tumor.
However, if the bloating appeared in the past couple of days, it is highly unlikely that it’s caused by a tumor, since tumors take more time to develop.
The best way to confirm or rule out tumor growth in a Betta is by taking the fish to a vet.
Tumors can be both internal and external. When they are internal, there isn’t any real way to detect them by just looking at your Betta.
In both cases, they can press against the organs of a Betta and cause further health issues, such as troubled swimming, difficult breathing, and swim bladder disease.
Additional symptoms might be a lethargic mood and a lack of appetite.
A tumor is really not curable, so what I can recommend here is providing your Betta fish with a comfortable life.
Keep the fish in a well-maintained aquarium, feed it with delicious, preferably live, food.
It should be noted that there are plenty of cases where the fish lives with a tumor for up to three years. This is because tumors do not affect a Betta’s ability to eat, swim, or breathe.
9. Not enough exercise
On rare occasions, the lack of enough swimming might cause bloating through constipation in Betta fish.
A Betta needs space to properly exercise its fins and whole body muscles. Be sure that your Betta has a big enough fish tank to explore, regardless of whether it lives alone or with tank mates.
Some people prefer 2.5 gallons tanks, others say every size smaller than 5 gallons is not big enough for the Betta fish.
My personal opinion is that a 5-gallon tank is the minimum aquarium size for Betta fish. Many experienced fish keepers would agree with me here.
If you think your Siamese fighter lacks enough movement, you can occasionally put a mirror in front of it. When the fish sees its reflection, it will start flaring its gills at it, which is a form of exercise.
You can do this for 1 to 2 minutes every other day.
Don’t go over the suggested time period, and do not leave the mirror in front of the tank.
As with all things the dose makes the poison.
Too much flaring is stressful for Betta fish and can actually weaken their immune system.
10. Malawi Bloat Disease
In rare cases, the stomach of a Betta fish could become swollen due to a disease known as Malawi Bloat.
Though research has been done, the origins of Malawi Bloat are still unknown.
If the condition is not treated, it will advance and apart from the swollen belly, you will see your fish having trouble with getting enough air.
Your Betta will spend more and more time on the surface of the tank, gasping to get some oxygen.
Also, the fish may get lethargic and lose any interest in food.
Its poop will become white and stringy (which is a good sign that Malawi Bloat is the result of an internal parasite).
Before you conclude that your Betta has Malawi bloat, make sure to rule out bacterial and roundworm infections.
The bad news is that if your fish has Malawi bloat, it will likely not end well.
Usually, once it’s diagnosed, it’s already too advanced for anything to be done, but some users report success with Mardel’s Clout.
Clout is a very strong medicine and should be administered with great caution as overdoses can be lethal to aquarium fish.
Don’t mistake symptoms for causes
There are some persistent factual mistakes that have been circulating in this hobby for quite some time now.
More often than not the 2 conditions described below will be cited as a “cause” for bloating in Betta fish.
In fact, they are merely symptoms of the actual cause.
1. Swollen Swim Bladder
The swim bladder is a gas-filled organ that regulates buoyancy in Betta fish. If for some reason, it becomes swollen, it starts pressing against the stomach of the fish, which manifests as a bloated belly.
A swollen swim bladder in Betta fish can be the result of multiple underlying conditions such as:
- high nitrate in the aquarium water with anything over 20 ppm of NO3– for continuous periods of time
- a bacterial infection that causes the swim bladder to collect fluid and expand
- gulping excessive air during eating non-sinking fish food, also known as air bloat
Each underlying condition and its symptoms might affect the swim bladder of Betta fish, and therefore their buoyancy.
If your Betta has a swim bladder disorder, you will see that it’s not swimming but rather floating upside-down at the aquarium’s surface.
It might also sink to the bottom or swim on one side.
At this point, apart from the bloated abdomen, a Betta fish will often refuse to eat.
In some cases where the swim bladder is swollen because of poor water quality, the spine of the fish could become curved.
Before I continue, I think it’s important to make something clear.
Swim Bladder Disorder is more of a consequence rather than a cause for belly bloat in fish. An enlarged swim bladder may cause bloating in Betta fish, yet a swollen belly can become the reason for Swim Bladder Disorder.
Now, you need to find the reason behind swim bladder issues and treat them accordingly.
If it is constipation due to overfeeding with low-fiber foods, you need to fast your fish for a couple of days and introduce fibers from insect exoskeletons in its diet.
You can also move the Betta to a hospital fish tank or give it therapeutic baths with Epsom salt. Those will relieve the swelling of the belly.
For parasites, follow the instructions above and use the right medications or simply consult with a fish vet.
Don’t forget to assess the water parameters of the aquarium and make changes if needed.
Liquid-based test kits such as API’s Freshwater Master Test Kit are superior to strips. Stips will be off and do not give a precise measurement of the water’s parameters.
2. Impaired fluid retention – Dropsy
If left untreated, bacterial infections or internal parasites may result in abnormal fluid retention in Betta fish.
This condition is also known as Dropsy and in its early stages, the fish starts to hold fluids in its abdominal area, which then expands.
This results in an extremely bloated belly for the Betta fish.
To identify Dropsy in Betta fish, check for the following symptoms:
- bloat in the abdominal area which later spreads to the whole body
- sticking scales that give a pinecone outer texture to the Betta fish’s body
- lack of appetite
- pale coloration
- curved spine (rarely)
- difficulties with swimming
- rapid breathing and gasping for air.
Now, I must make clear that, same as the swim bladder disorder, Dropsy (or edema) is a symptom, rather than a disease.
Sick and stressed fish often end up with Dropsy as a final stage of some untreated disease.
Dropsy is often labeled as incurable. However, if it is caught in an early stage, successful treatment with Epsom salt and antibiotics may be possible.
Epsom salt will alleviate the swelling and the antibiotics will take care of the infection itself.
A Betta fish developing Dropsy indicates damaged kidneys or liver, and sometimes both.
Kidneys are responsible for passing water through the urinary tract in fish.
When they are malfunctioning, however, the fish starts retaining a large volume of fluids and the body swells, usually starting with a big abdomen.
When I was first doing research on fluid retention in fish, I found that more often than not the condition is caused by some type of “gram-positive” bacteria in the kidneys.
Gram-positive is a classification of bacteria species based on their cell walls.
For this reason, I usually treat the condition with an antibiotic that targets gram-positive bacteria specifically.
Apparently, some good antibiotics for the purpose would be erythromycin and amoxicillin, as described in this summary by the University of Florida.
Erythromycin can be found in a product known as Mardel Maracyn.
However, I’ve found that amoxicillin works better in this case and generally has a higher chance of success than erythromycin.
You can find amoxicillin at Chewy or any other large online store for pet supplies.
Now onto the treatment itself.
You will need 1 hospital tank where you’ll treat with antibiotics and one tank where you’ll carry out the Epsom salt baths.
Though amoxicillin won’t harm the Gram-Negative nitrifying bacteria in your main aquarium it may disturb the overall ecological balance established by other Gram-Positive bacteria.
Anyway, make sure the water in both tanks shares similar parameters to avoid shocking the Betta fish in between relocations.
Follow the instructions on the packages of both the antibiotic and the Epsom salts.
For the salt baths, use 1 tablespoon of Epsom for each gallon of water and let the fish swim in the mixture for about 20 to 30 minutes.
Know that though Epsom salt may be relieving for the fish, there isn’t any guarantee that it will reduce the bloating.
Wasys to prevent a bloated belly in fish
The best possible way to prevent your Betta fish from becoming bloated is taking proper care of it and the fish tank from day one.
Feeding your pet fish with high-quality food is essential.
Reduce pellets and flakes to a minimum and interchange them with live, or freeze-dried live food.
You should also fast your fish at least once a week.
Perform the regular water change to maintain a quality aquarium environment.
Don’t forget to check the ammonia and nitrate levels, as spikes in those can rapidly induce stress in the fish.
Stress, on the other hand, can and will increase the chances of disease.
You can either do frequent water chemistry tests with a liquid-based test kit or set up an Ammonia Alert indicator that will constantly track NH3 levels in the aquarium.
Avoid placing sharp objects into the tank, as sometimes this can lead to injuries, more stress, and further health issues.
The same goes for the tank mates – Betta fish are aggressive by nature and need some personal space.
For this reason, it is very important to choose the fish they share the aquarium with carefully.
Anyway, give your Betta enough space to swim around and to exercise its body muscles.
Although lots of people choose 2 or 2.5-gallon aquariums for their Betta pets, this is not really enough space for a happy life.
My piece of advice here would be to keep a Betta in a tank that holds no less than 5 gallons of water.
Bloating in Betta fish is not an uncommon sight.
While a swollen belly may look scary, in most cases it’s relatively harmless.
However, if the harmless conditions are ruled out, an adequate treatment for an underlying bacterial infection may be your best bet.
Leave me a comment below if you’d like to receive more answers.