Swollen Fish – Dropsy Disease Causes & Treatments

When you decide to venture into the aquarium hobby, you should be ready for anything coming out of it, including diseases.

Inasmuch as you may look forward to a vibrant fish tank, you should also be ready to identify and solve any problem that might arise from within.

One of the problems you are likely to encounter is freshwater fish diseases is dropsy.

In this article you can learn about dropsy disease and how you can prevent it to keep your freshwater aquarium fish healthy throughout.

Swollen Fish - Dropsy Disease

Swollen Fish – Dropsy Disease

What is Dropsy?

Dropsy is a name used to describe a condition known today as ascites or edema. This is the swelling of some soft tissues in a fish’s body cavity.

The swelling may occur in the abdomen or other parts of the body.

This happens more often because of the accumulation of fluids or water within the affected body region.

The name might have been derived from the Middle English noun, ‘dropsie’ or from a French word ‘hydropse’ or better still, from a Greek phrase ‘hydrops’, meaning water (hydro).

The term dropsy describes the swelling problem that commonly affects aquarium fish. Most of the affected fish appear to have swollen bellies that seem to drop down.

In most cases, the condition is referred to as ‘bloat’.

Can You Treat Fish Dropsy?

Unlike ich (white spot disease), fish dropsy is not easily curable. This is only possible when the infection is diagnosed at the right time and treated immediately.

The whole treatment process aims at correcting all the underlying problems while providing supportive care to the affected fish.

Dropsy Disease Causes & Symptoms

Dropsy is a collection of symptoms brought about by a bacterial infection, The bacteria is commonly found in the aquarium environment. Any fish can be exposed to this bacteria but that should not be a cause to panic. Only those with a weak immune system will be affected in the process.

Also, the disease can affect all fish in the tank if they are under stress. But it’s also possible for a few fish in the tank to be affected when drastic measures are taken at the right time. So, what causes dropsy disease in the freshwater fish tank?

Dropsy disease is caused by Aeromonas bacteria. This is one of the gram-negative bacteria commonly found in most of the fish tank environment. They are referred to as gram-negative bacteria because they don’t take any stain when undergoing the usual identification of different species of bacteria.

But the bacteria will only affect and cause serious infections in those fish that have a compromised immune system. The infection can be triggered by stress due to a number of factors which include:

  • Nitrate or ammonia spikes
  • Poor tank water quality
  • Stress resulting from transportation
  • Poor nutrition
  • Changes in water temperature
  • Aggressive tank mates
  • Other illnesses

Short-Term exposure to any type of stress won’t compromise the fish’s ability to fight infection. The exposure to stress should take longer or involve multiple stress factors in rapid succession to weaken the immune system of freshwater fish.


Symptoms of fish dropsy disease vary widely. While some fish will exhibit swollen abdomens, others will display skin lesions and so on. Due to these variabilities in symptoms and signs, it is extremely difficult to diagnose this disease.

But several symptoms can be observed, both behavioral and physical as follows:

  • Swollen abdomen
  • Scales form a pinecone-like appearance
  • Bulging eyes
  • Paleness on gills
  • The anus turns red and becomes swollen
  • Pale and stringy feces
  • Ulcers on the entire body, especially along the fish’s lateral line
  • A curved spine
  • Clamping together of fins
  • Redness of the fins and skin
  • General lethargy
  • Loss of appetite
  • Swimming close to the surface

The symptoms become more serious as the infection spreads. In most cases, the fish’s internal organs such as the kidneys and liver become affected. Anemia occurs, making the gills pale due to lack of enough blood.

The increased amount of fluid in the abdomen causes the organs to move aside, thus affecting the spine. All these symptoms indicate a severe infection of fish dropsy disease.

Treating Dropsy in Fish

The treatment aims at correcting all the underlying problems as well as providing proper care to the affected fish. Below are the most effective ways of treating fish dropsy disease:

Isolate the affected fish and place them in a separate tank (hospital tank). Water temperature in the hospital tank should be monitored to ensure that it remains almost the same as that of the first tank.

Add  2 ½  teaspoons of salt for every 10 gallons of clean freshwater in the hospital fish tank. The mineral (magnesium sulfate) found in the salt will remove excess water from the sick fish’s body.

The excess water is actually the fluid caused by the dropsy disease and it makes the abdomen to swell.

Provide your sick fish with foods rich in antibacterial fish food. You can purchase prepared antibacterial food or prepare your own by adding a 1% mixture of any type of fish food to an antibiotic such as tetracycline or chloromycetin.

Keep on providing your sick fish with antibiotic fish food while keeping an eye on it for a period of 7 to 10 days.

If there is no improvement after several days of treating your fish, then treat the tank water using Maracyn-2. This type of medication is effective in controlling bacterial infections in the fish tank and its readily absorbable through the skin.

Should you realize that there is no improvement after 10 days of treatment, then it is most likely that the cause of fish dropsy disease is not bacterial.  If the salt bath and antibiotics are not bringing positive changes, there is little you can do to save your sick fish.

Prevent Fish Dropsy

Just like other types of diseases, prevention is the only reliable cure. Through prevention, all factors contributing to the susceptibility to infections can easily be prevented.

One of the factors causing fish in the tank to become stressed is the poor water quality. For that reason, tank maintenance is the ultimate solution to this problem.

Below are the steps to take into account to prevent the fish dropsy infections:

  • Make sure that tank water is changed regularly
  • Maintain cleanliness in the tank
  • Keep the filter clean all the time
  • Test tank water from time to time to ensure that all parameters are right for your fish
  • Remove the waste from the substrate using a gravel vacuum
  • Don’t overcrowd the tank
  • Don’t give your fish excess food
  • Make sure that you use flake food in less than a month after opening the packages
  • Change your fish’s diet regularly

Proper tank maintenance and feeding the fish on a healthy diet are the two most important factors that can prevent fish dropsy disease.

Is Dropsy Painful for Fish?

Yes. Given that the disease causes swelling in some parts of the affected fish’s body, it is likely that this condition will cause some pain to the fish.

Is Dropsy Contagious to Other Fish?

Dropsy fish disease is not contagious. But if one fish becomes infected, other tank mates, especially those of the same species will be at great risk of being infected as well.

Also, the disease can affect any type of fish that has a compromised immune system.

Should You Euthanize Fish with Dropsy?

According to some experts, you can euthanize all affected fish in order to prevent the spread of the disease to other healthy fish.

The need to carry out euthanization is prompted by the difficulty with which the disease is cured.

So, it is advisable to apply preventive measures as the best solution to treating the disease even before it spreads further.

Euthanization is one of the most effective ways of preventing the spread of dropsy fish disease.

Is Fish Dropsy Contagious to Humans?

Fish dropsy disease is not contagious not only to other fish but to humans as well. Apparently, there are no known cases of dropsy transmission and infections to humans.

This is because the pathogens responsible for this condition are mainly found in the tank water environment. Besides, the disease affects those fish that are exposed to stress for a long time.


Sadly, dropsy fish disease is a fatal health condition affecting fish in the tank. The condition is caused by many factors, key among them the bacteria known as Aeromonas.

But you should keep in your mind that stress contributes more to the infection and spread of dropsy fish disease in the tank.

In this regard, you must ensure that your fish remains stress-free throughout to avoid compromising their immune systems.

However, the best method of preventing this disease is by keeping your freshwater fish healthy as well as maintaining cleanliness in the tank.

If the fish happens to contract this disease, take drastic measures at the right time and treat it using the recommended antibiotics.

Sometimes, you may act quickly in a bid to control the disease, but there are cases where you may not be able to save your freshwater fish.

Otherwise, you may seek assistance from your local veterinarian if the situation gets out of hand.

Fishkeeping   Updated: October 18, 2019
avatar Hello, my name is Fabian, and I am the Chief Editor at Aquarium Nexus. I have over 20 years of experience in keeping and breeding fish. The aquarium hobby brings me immense joy, and I take great pleasure in sharing my experiences with others.

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