How to Cure Sunken Belly in Aquarium Fish?

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Seeing a fish with a bloated belly is already a common occurrence and one that doesn’t raise too much concern. Most fish will experience bloaty guts at some point, either due to constipation, parasites, swim bladder issues, etc.

Other times, an inflated abdomen is nothing more than a sign of pregnancy.

But things are different when discussing a sunken belly. The sight of a sucked-in abdomen is unusual for most novice aquarists and, as a result, more concerning.

While this condition isn’t typical to one fish species only, it appears that African cichlids are more prone to encounter it.

Today, we will dive into the causes and symptoms of sunken bellies in African cichlids and other fish species that may struggle with the condition.

Causes of Sunken Stomach in Fish

Not all fish will display the same appearance, but the condition generally showcases similar symptoms. The belly is only slightly sucked in in some, while others will display more aggressive effects, depending on the causes.

These include:

  • Starvation – This is atypical since it shouldn’t happen if you feed your fish correctly and on schedule. The problem arises specifically among African cichlids since you most likely have several of them in the same tank. African cichlids are notorious for preferring to live in pretty crowded environments with a lot of tank companions. They are also extremely competitive when it comes to food, reproduction, space rights, and hierarchy, making their society more volatile overall. So, it’s not uncommon to have some cichlids starving due to higher-ranked ones bullying them into submission. It’s why it’s essential to monitor your cichlids’ interactions and social behavior.
  • Hexamita or other parasites – Hexamita is the pathogen responsible for the Hole in the Head syndrome. This disorder is the result of the parasite invading the fish’s organism, multiplying, and causing significant tissue damages to the point where it can kill the host. Other parasites may be responsible for the sunken belly effect as well, especially intestinal worms. Interestingly, many of these pathogens are even present in healthy fish but are kept under control by the fish’s robust immune system. They will only begin to multiply when the fish’s immune system registers a fall due to environmental conditions, temperature fluctuations, or other diseases. In this case, a medication-based treatment may be necessary to fix the issue.
  • Fish tuberculosis – This is a devastating fish disease that probably ranks as the most dangerous in the tank world. The culprit is the Mycobacterium pathogen that’s extremely difficult to eradicate since it has a protective coating rendering it immune to most medications. So, it’s safe to say that fish tuberculosis is contagious and nearly impossible to treat, most often resulting in the host’s death. It can also transmit from fish to humans via open wounds having contact with the infected fish or water. Some of its symptoms include lethargy, sunken belly, body ulcers, skin lesions, open sores, losing scales, spinal deformities, etc. The problem is that many of these symptoms are also found in other, more benign conditions, which may lead to misdiagnosis, allowing the disease to aggravate. Late-stage tuberculosis is uncurable and will always result in death, so euthanizing the sick fish is necessary to spare its suffering and protect the rest of the population.
  • Nutritional deficiencies – Fish will display a variety of health problems due to improper dieting. Vitamin and mineral deficiencies will cause an array of symptoms, including sunken bellies, poor growth, scoliosis, anemia, cataracts, etc. In many cases, improper nutrition will kill the fish fast, especially if complications arise along the way. Your fish’s nutritional deficiency will create different symptoms, depending on the nutrient lacking from its diet.

With so many causes and a variety of overlapping symptoms, it can be quite difficult to diagnose your fish’s condition accurately.

But you need to do it and fast. Some of the underlying causes are contagious and could spread to other fish fast.

How to Treat Fish with Sunken Belly?

Addressing the sunken belly syndrome consists of 2 primary phases:

  1. Quarantine – First, you need to separate the sick fish from the rest of the population. This is especially true for African cichlids since they tend to crowd together in larger societies. In their case, one contagious disease could wreak havoc among their ranks. Make sure the hospital tank offers stable and optimal parameters, similar to the conditions present in the main tank.
  2. Assessing the disorder – Once the fish has settled in the treatment tank, the next important phase is diagnosing the condition. An accurate diagnosis is key to painting a clearer picture of what’s going on. The process will allow you to determine the type of the disease causing the sunken belly effect and the disorder’s severity and progression. This step will allow you to adopt a personalized treatment blueprint to speed up your fish’s recovery.

After you’ve determined the cause of the sunken belly, the next phase in the treatment process. This part involves addressing each condition according to its profile.

In this sense, we have:

  • In case of parasites or bacterial infections – Use medication. Seachem Paraguard is perfect in this sense. This product is perfect for addressing an impressive variety of ectoparasites, fungi, bacteria, and other dangerous pathogens responsible for skin lesions and severe tissue damage. Paraguard contains no methanol or formaldehyde, so it won’t change the water’s pH, keeping your fish in a safe, clean, and stable environment throughout the treatment. It’s a must-have for addressing viral infections that could spread between other fish fast, as it promotes quick recovery via a potent anti-parasitic effect.
  • In the case of fish tuberculosis – Fish tuberculosis is pretty much uncurable in late stages, at which point you only euthanasia as a viable option. However, you could effectively address the disorder in its early phases, provided you can diagnose it in time. I recommend speaking to an expert vet to diagnose the condition accurately and lay out the ideal treatment plan. Always quarantine your sick fish at the first worrying symptom, whatever the treatment may be. Fish TB is highly contagious and could spread fast to the entire fish population.
  • In case of nutritional deficiencies – If you’re a novice aquarist with little experience in handling tank fish, especially more exotic species like African cichlids, you could easily mess up their diets. Cichlids require a rich and diverse diet, and you need to find ways to diminish the impact of food-related competitive violence. I suggest speaking to a cichlid professional to figure out the ideal meal plan in terms of contents and feeding pattern. Your cichlids should rebound fast once they start getting adequate and sufficient food.

Best Medication for Sunken Belly Fish

Seachem Paraguard is my favorite in this area.

It is one of the most popular fish medications you can find for several reasons:

  • Efficiency – Paraguard tackles most external parasites at any point during their life cycle. This makes it effective against disorders like fin and tail rot, Ich, and other viral pathogens that could even cause internal infections. Two weeks are generally sufficient for Paraguard to eliminate all traces of viral organisms from the water successfully.
  • Protective qualities – The product contains specific polymers that protect the fish from further infections. These also strengthen their immune systems, allowing their own bodies to fight back against the infections and speeding up recovery.
  • Doesn’t alter the water’s pH – This is an important plus since many products in the same category will alter the water’s pH at times. This is less than ideal when talking about cichlids which are notoriously pretentious about their water parameters.

Seachem Paraguard is a great choice if your fish showcase parasite or bacterial-related sunken bellies and require immediate treatment. Just make sure you quarantine the fish first and that you don’t use the product in reef aquariums or on specific fish species. These include loaches, sharks, eels, and even invertebrates since they are more sensitive to pretty much any type of medication.

Ideally, the treatment shouldn’t last more than 2 weeks. That’s how much time Seachem Paraguard needs to eliminate all traces of viral pathogens from the water. In some cases, your fish might require a bit more time to heal and recover.

Make sure you monitor their progress during the treatment to see when they’re ready to leave the hospital tank.

Will Sunken Belly Disease Kill My Fish?

It depends. The most honest answer would be ‘not necessarily.’

But it can happen, depending on factors like:

  • The condition’s triggers – If your fish has TB, the condition will progress fast, and it’s almost always deadly, especially in advanced stages. In this situation, all you can do is quarantine the fish, offer adequate treatment, and hope for the best. If your fish doesn’t show any improvement within several days to a week, I suggest euthanasia as the best alternative.
  • The fish’s profile – Your fish’s age, immune system, size, and genetic makeup will all make the difference between life and death. Fish with immunocompromised systems will fall sick more often and show increased difficulties in recovery and healing. Expect the same results if the fish is old and its immune system isn’t as effective as it once was. The fish’s genetic makeup will also weigh in heavily in the balance since some fish have weaker immune systems by means of genetic inheritance.
  • The quality of care – Sometimes, even mild cases of sunken belly will turn deadly if the fish lacks proper care during the recovery phase. So, your actions are just as important as your fish’s ability to fight back. Diagnose the condition early and provide adequate treatment to improve your fish’s recovery chances.

In more severe cases, the sunken belly syndrome will cause death, and there will be nothing you can do to prevent it.

At that point, you must recognize the likely outcome and act to protect the rest of the fish population.

I recommend quarantining the fish, monitoring its progress during the treatment, and applying humane euthanasia if the treatment doesn’t work.

How Long Can Fish Live with Sunken Belly?

There’s no telling how long your fish can survive with a sunken belly syndrome, even when knowing the cause.

Fish are different and will often react differently to various disorders. While some can go weeks without food, others will cave in within several days or even sooner if they’re older or develop health complications along the way.

This is why treating sunken belly in its early phases is so important in the larger picture. A fish with a sunken belly is a worrying sight for good reasons. You should immediately investigate the fish to determine the cause of its problem and find an adequate treatment soon.

Why My Fish with Sunken Belly Is Not Eating?

The lack of appetite could be a symptom of multiple disorders and conditions, including parasites, bacterial infections, digestive problems, etc.

Basically, anything that stresses out the fish will also kill its appetite and influence its behavior. Fish with sunken bellies will display lethargy, poor eating or complete lack of appetite, hiding behavior, aggression, poor swimming patterns, etc.

This goes to show that diagnosing your fish’s condition based on the lack of appetite is next to impossible. Instead, you need to consider multiple other symptoms to make sure you’re getting the right diagnosis.

Otherwise, you might apply the wrong treatment, allowing the disorder to aggravate and even spread to other fish.

Are African Cichlids Prone to Sunken Stomach?

Yes, they are more prone to this condition than other fish. African cichlids are rather pretentious about their diets, environmental setup, water parameters, and even tank mates.

They are also sensitive to dangerous chemicals that might poison their water, like ammonia, nitrites, chlorine, and chloramines, to name a few.

Their increased sensitivity to these aspects is what makes cichlids unfit for novice aquarists since they demand extra care and a stricter maintenance routine.

You should provide your cichlids with impeccable water conditions and a nutritious diet to prevent conditions like sunken belly syndrome over the years.

Doing so will also increase your cichlids’ quality of life and prolong their lifespan considerably.


Prevention is always key to addressing the sunken belly syndrome effectively.

In this sense, I recommend several strategies:

  • Quarantine newcomers – Never introduce any new fish into the tank without a proper 2-week quarantine period at a minimum. This will allow you sufficient time to assess the fish’s health and make sure it’s free of parasites, bacteria, or other dangerous and contagious diseases.
  • Avoid certain worms and feeder fish – When it comes to cichlids, you should choose their live food very carefully. I recommend avoiding tubifex worms and certain feeder fish notorious for being infested with parasites and various other pathogens. And never feed your cichlids wild fish since these are almost always packed with intestinal worms and dangerous bacteria.
  • Always consider early quarantine and treatment – You should react at the first sign that something’s wrong. If your cichlid displays unexplained changes in color, refuses food, hides constantly, and displays lethargy, quarantine the fish immediately. I cannot overstate the importance of early treatment when it comes to addressing conditions like sunken belly syndrome.
  • Provide increased quality of life – A nutritious and diverse diet are necessary for any cichlid species, especially African ones. Make sure your cichlids don’t lack any nutrients in their diets, and always adjust their meal plans if they do. You might want to consult with a vet in this sense. When it comes to water quality, nothing beats stability. Offer your cichlids a clean, healthy, and fresh environment with stable parameters, and they will thrive.

Above all, knowledge is what will help you address the sunken belly syndrome more effectively, decreasing the death toll among your fish.

Author Image Fabian
I’m Fabian, aquarium fish breeder and founder of this website. I’ve been keeping fish, since I was a kid. On this blog, I share a lot of information about the aquarium hobby and various fish species that I like. Please leave a comment if you have any question.
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