Dropsy in Fish: Causes, Symptoms & Treatment

Fish dropsy is an abnormal physiological condition of fish caused by the accumulation of unnecessary fluids in the abdominal cavity.

Dropsy is treated as diseased condition or a state not disease. But the bloated appearance makes owners and farmers puzzled somewhat.

Dropsy may be caused due to several reasons. Environmental factors (i.e., poor water quality, pollution), bacterial and viral infection, physical injury are major causes of abdominal distension. 

Dropsy in Fish

What is Dropsy? (Is Dropsy is a Disease)

Dropsy is a serious and potentially deadly diseased condition observed in different disease stages.

The last stage of the bacterial disease is Dropsy.

The bacteria that comprise the Dropsy infection eventually infiltrate the fish’s kidney and cease it functioning properly.

The victim of Dropsy does not have any way to get rid of body fluids, so it becomes distributed throughout the body of the fish.

Fish suffering from dropsy will have a bloated, protruding belly and scales that stand out from the body.

But why was it called dropsy?

It turns out that the ancient Greek word hydrsoe, which means water.

Causes of Dropsy in Fish | How Does Dropsy Occur

Poor Water Quality

Poor water quality causes nitrite spikes. Sudden changes in water parameters ( pH, temperature, hardness) induce stress conditions.

Nitrogenous waste products imbalance the optimal water chemistry that create stress for fish.

In excess level it creates severe stress to fish and initiates further disease. 

Nitrate is harmful for fish. Nitrite hamper the oxygen transport system in respiratory system that indirectly damage internal organs like kidney and disrupt the body’s osmotic balance.

Poor water lower immune defense mechanism for long run and fish faced extreme stressed condition.

Temperature Shock

A drop in water temperature causes stress. Transportation and improper diet also cause stress. Aggressive tank mates in the fish tank and other diseases cause stress. The temperature 70-80 degree F is good for tank.

Bacterial Infection

Dropsy is a severe infection caused by bacteria of the genus Aeromonas and Pseudomonas fluerescens.

Dropsy is caused by a gram-negative bacterium of the Aeromonas genus. Aeromonas hydrophila, Aeromonas sobria, Aeromonas caviae are the causative agent of dropsy fish.

These bacteria cause disease in fish that already have an impaired immune system. The bulging symptoms in different tissues of fish are called dropsy.

Viral Infection

Several grouped of fish viruses cause internal hemorrhages and create internal liquids that accumulate in abdominal cavity.

Parasitic Infestation

Densely helminth parasites may be a reason of abdominal distension in fish. Several internal parasites harbor in gut swell the stomach and intestine to bulging out.

Organ Dysfunction

The dysfunction of kidney and liver generate the viscous fluid in abdomen and create a diseased condition. It causes absorption of water in body cavity.

Improper Diet

Imbalance diet may cause this disorder in different species.


Pathogenic microorganism transmitted through water. The disease is somewhat contagious.

Susceptible Host

Freshwater cultured and aquarium fishes highly susceptible to this condition. The condition appears in different aquarium ornamental fish species.

Pet fishes are affected most as they remain in small closed condition. Betta fish and goldfish dropsy is common in fish tank.

Dropsy also occurred in pond fish. Freshwater fish dropsy is common in the world.

Signs and Symptoms of Dropsy in Fish

  • Abdominal distension or swelling. Fishes are observed with bulging abdomen caused by a buildup of fluid within the tissue
  • Extensive outward (Protruding) scales makes fish look like pinecones
  • Fins clamped down against the body means the sick fish struggle to swim
  • Other symptoms include lethargic behavior and swimming erratically
  • Faces become stringy because the fish are losing weight
  • When internal organs swell up, they push the other organs out of place
  • Sometimes the fish’s back curves due to the swelling
  • Loss skin and gill natural color, gill become paled and faded 
  • Loss of appetite and become lethargic
  • Excess mucus production
  • Anal region become swollen

Diagnosis of Fish Dropsy

  • Water Quality Test: Water quality kit measure the nitrogenous substances concentration in water and help to find the causes.
  • Behavioral Changes: This may be accompanied by other symptoms such as discolored scales, lethargy, and loss of appetite.
  • Clinical Diagnosis (Changes in Appearance): Clinically in your visible eye you can assume the dropsy condition observing the abdominal region. Is it distended or normal to the body shape. The first sign of dropsy is usually a swollen belly.
  • Microbiological Diagnosis: Pure culture of abdominal fluid is another method to identify this disorder and causing agent.
  • Molecular Diagnosis: For further identification of causative agent different molecular test (PCR, ELISA) may performed.

How To Treat Dropsy in Fish | Fish Dropsy Treatment

Salt Treatment

Epsom salt at the rate of 1-2 teaspoons per gallon water for 15-30 minutes are recommend to get rid of the condition.

Fish exchange ion through osmosis mechanism by skin and gill. Salt treatment initiate the process and help to draw out excess fluid from belly.

Salt also clean the water acting as disinfectant against bacteria and parasite. If not recovered destroy the fish and change the water if possible.

Water Exchange

Remove severely affected fish and exchange the water at a rate of 25 to 50% based on the severity of the disease and water quality degradation.

Measure the water quality parameter specially nitrogenous substances like nitrite and ammonia using water quality kit.

Antimicrobial (Antibiotic) Treatment

Antimicrobial agent specially naturally or synthetic antibiotics use reduce the bacterial infection and recover fish from this disorder.

Antibiotics can be added to the tank water or given to the fish orally. Antibiotic should your according to their body weight (1-2%).

First you have identify the bacterial group responsible for this condition. Aeromonas grouped are bacteria are broadly responsible for this.

Feeding infected fish antibacterial food is very effective in treating dropsy. The recommended dose for oxytetracycline is 3gm/ kg feed.

Erythromycin, Amoxicillin, and Streptomycin are also effective in treating dropsy in fish. Vitamin C is also used as feed medication along with antibiotics.

A study found the antimicrobial resistance of the isolated bacteria was higher with Oxytetracycline (OX) and lower with Ciprofloxacin (CIP). 

Increase Temperature

Raising temperature may reduces the severity of this disease. Raise temperature 3 to 5 degree fahrenheit.

How To Avoid Dropsy in Fish?

  • Provide healthy & adequate feed: A well-balanced diet will help keep their immune system strong and help to prevent diseases like dropsy. Feed adequately, don’t overfeed.
  • Quarantining new fish: New fish can carry diseases that can infect your other fish, so it’s important to quarantine them first.
  • Regular water monitoring: The water quality needs to be regulated weekly. Partial water exchange of tank or aquarium is vital to reduce disease outbreaks. Water quality parameters are checked and maintained by performing weekly water changes. Environmental conditions must be free from pollution and contamination.
  • Avoid high stocking density: Follow optimum stocking recommendations for your farm unit and aquarium.
  • Remove bottom waste from tank: Regularly remove the waste or debris from tank bottom through siphoning or using any other ways.

Are Dropsy and Edema the Same Thing?

The accumulation or buildup of fluids in different tissues of fish known as edema. The condition dropsy is synonyms (technically known) to the term edema.

Edema categorized into three types;

  1. Ascites: Accumulation of fluid in abdominal cavity.
  2. Exophthalmia: Accumulation of fluid in eye socket.
  3. Pinecone scale: Accumulation of fluid in scale pocket-Pithing

Frequently Asked Questions (FAQs)

Is dropsy contagious to other fish?

Dropsy is a bacterial infection that can cause fish to swell up and look bloated. The disease is not contagious to humans, but it is contagious to other fish.

If you have a fish that has contracted Dropsy, you will need to isolate it from the rest of your fish and treat it with antibiotics.

Can humans catch dropsy from fish?

There is no evidence that humans can contract the disease from fish, it is still important to take precautions when cleaning or handling fish with dropsy.

Always wear gloves and wash your hands thoroughly after contact with infected fish. If you think your fish may have dropsy, consult a veterinarian immediately.

Can a fish recover from dropsy?

Dropsy is caused by a bacterial infection and can be treated with antibiotics.

If a fish has contracted Dropsy, it is important to isolate it from other fish to prevent the infection from spreading.

Is dropsy painful for fish?

This includes the fact that fish with dropsy often have difficulty swimming and can be seen rubbing their bodies against the sides of the tank or other objects in an attempt to relieve the pain.

Can a fish die from dropsy?

Dropsy is a condition that could be often fatal for fish. In severe stressful condition mortality must occurs in fish unit and fish tanks. Research found that in 98% cases aquarium fish die.

How long does dropsy take to kill a fish?

A case of dropsy in a fish can be fatal within 1-2 weeks if not treated properly and promptly.
If you notice any of these signs in your fish, it is important to seek treatment immediately in order to give your fish the best chance possible for survival.

Are fish with dropsy active?

Dropsy is a condition that affects fish where they experience an abnormal buildup of fluid in their tissues. This can make the fish uncomfortable and less active.

Should I kill a fish with dropsy?

Primary treatment may recover fish from bloating condition but in case of severe infection and internal damage it’s difficult to cure affected fish. In that case you should separate and kill these affected individuals.

Can dropsy go away?

Dropsy is not an easily cured disease and treatment is necessary to get rid of dropsy in fish.
While some fish may recover from dropsy on their own, most will need some form of medical intervention.

When is it too late to treat dropsy?

Visible signs were observed after a organ failure of fish. It would be to late to treat dropsy if internal organ damaged occurred.

How do I clean my fish tank after dropsy?

If your fish has dropsy, you’ll need to clean their tank to prevent the spread of the disease.
Wash the tank, plastic plants and gravel in hot water (no soap). Bleach can be used on the tank and plants. Rinse the tank components with water.


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