Dropsy in Fish

Causes, Treatment, and Prevention

Female guppy with dropsy pinecone scales

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Dropsy (sometimes called bloat) is not a disease but a condition caused by an underlying health issue like an infection, parasites, or liver dysfunction. It involves the accumulation of fluid in a fish's body, giving it a swollen or bloated appearance. Often exacerbated by environmental stressors, dropsy should resolve when the stress is relieved and the underlying illness is treated. Of course, the prognosis depends on the severity of the illness and its response to treatment.

What Is Dropsy?

Dropsy refers to a condition in which fluid accumulates in a fish's body. Technically referred to as edema or ascites, dropsy is a sign of malfunctioning kidneys and/or gills due to an underlying health issue.

Symptoms of Dropsy in Fish

Depending on the underlying cause of kidney and/or gill malfunction, you may see a variety of physical symptoms. Dropsy, as an isolated condition, is associated with various forms of swelling.


  • Swollen belly
  • Protruding scales
  • Bulging eyes
  • Pale gills
  • Increased respiratory rate
  • Swollen anus
  • Redness of the skin or fins

Swollen Belly

A fish with dropsy experiences rapid abdominal swelling, distinguishing the condition from weight gain or pregnancy. All of the internal organs will eventually become swollen and stop functioning. The fluid accumulation is caused by the inability of the kidneys and/or gills to eliminate water from the body, which is a result of the underlying health problem.

Protruding Scales

The internal swelling of dropsy causes a fish's scales to protrude and point away from the skin, giving the fish a "pine cone" appearance. Protruding scales may be present all over the body or only on parts.

Bulging Eyes

Swollen eyes indicate the presence of excess fluid that can't be eliminated from the body. The fluid causes pressure behind the eyeball, resulting in exophthalmia, usually bilaterally (both eyes).

Pale Gills

Excess fluid in a fish's body can cause its gills to distend and appear pale. Pale gills are associated with many diseases in fish and may be a result of the primary stressor or disease, not just dropsy.

Increased Respiratory Rate

To "breathe" oxygen, a fish inhales water, and oxygen is assimilated via the gills. If the gills are not functioning properly, the fish must work harder to take oxygen into its tissues. This effort is evident in a faster-than-normal respiratory rate.

Swollen Anus

If excess fluid is unable to leave a fish's body, it may build up in the intestines, causing internal and external swelling that may be seen in the anus.

Redness of Skin or Fins

As a fish's skin is stretched with excess fluid, small blood vessels may pop and pool in the skin and fins.

Symptoms of Dropsy

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Causes of Dropsy

Fluid accumulates inside a fish's body due to kidney and/or gill dysfunction that may be caused by one or more of the following:

  • Bacterial infection
  • Fungal infection
  • Parasites
  • Liver dysfunction

With chronic stress, a fish becomes vulnerable to infections. Generally, a single or short-term exposure to stress, known as acute stress, will not compromise a fish's ability to fight infection. In cases of illness, stress exposure usually occurs for an extended time.

Diagnosing Dropsy in Fish

If you notice signs of dropsy in one or more fish, call your veterinarian for help. Your fish has a better chance of recovery if you get a correct diagnosis and treatment early in its disease.

Your veterinarian will evaluate your fish's physical symptoms and the aquarium environment, which may include water quality testing. Poor water quality is one of the most common causes of illnesses that involve dropsy. Learning to test water quality in an easy way to keep your aquatic environment in good health and prevent stress in your fish. 

Dropsy is easy to identify by the swelling of a fish's body, but your veterinarian will also help identify the underlying cause and recommend targeted treatment.


With all fish illnesses, prompt diagnosis and treatment better a fish's chances of recovery. Treatment of dropsy must be geared toward correcting the underlying problem and providing supportive care to the sick fish.

Here is a list of treatments that may help:

  • Salt: A bit of salt in the tank water can aid in the osmotic balance of the fish by making the water salinity closer to the fish's blood salinity. That helps the fish expel accumulated water. A safe level of salt for most pet fish is 1-2 ppt. You will need to calculate a dose based on your tank's size and weigh your salt appropriately.
  • Clean water: If you have fallen off your maintenance schedule, the worst thing you could do for your sick fish is a massive water change. Never do more than a 50% water change at once, provided your pH is correct. If your pH is incorrect, you will need to do multiple small water changes frequently to slowly move your pH back to the correct range. Check your water chemistry regularly to ensure proper fish health, regardless of their disease status.
  • Antibiotics: If unsure about your fish's condition, consult your veterinarian about the type and amount of antibiotics to use.

Prognosis for Fish With Dropsy

Since it is a symptom and not a disease, dropsy is dependent on the state of a fish's underlying illness and will resolve if that illness can be successfully treated. Dropsy can be fatal due to the advanced stage of the underlying disease causing excessive swelling that leads to organ failure.

How to Prevent Dropsy

As with all diseases, prevention is the best medicine. Preventing chronic stress in fish is the best method to prevent dropsy. Because poor water quality is the most common root cause of stress, routine tank maintenance is critical. Factors to keep in mind include:

  • Test the aquarium water regularly to ensure it is healthy for your fish.
  • Perform regular water changes and keep up with your maintenance routine
  • Clean the filter regularly, but don't replace your media
  • Use a gravel vacuum to remove wastes from the bottom of the tank and remove your tank decor before using
  • Avoid overcrowding the tank
  • Do not overfeed fish; feed an appropriate diet
  • If you notice any signs of illness, check your water chemistry
  • Have a hospital tank ready for sick or new fish

Although taking all these steps cannot guarantee a dropsy-free system, they will go a long way to ensure the health and longevity of all your fish.

If you suspect your pet is sick, call your vet immediately. For health-related questions, always consult your veterinarian, as they have examined your pet, know the pet's health history, and can make the best recommendations for your pet.
Article Sources
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  1. Dropsy. Fritz Aquatics.