Dropsy in fish: symptoms, care and treatment

Dropsy is an ancient medical term that was once used to describe a state of swelling due to an accumulation of fluids in the tissues or cavities of the body, such as the abdomen. A fish with dropsy often has a swollen belly.

The disease is actually an infection caused by bacteria that are commonly found in all aquariums. As a result, virtually any fish species can be affected by dropsy.

However, healthy fish rarely get sick with this disease. Fish are sensitive only when their immune systems are compromised by some stressor.

 If all the fish in the tank are under stress, it is possible that the entire aquarium may be infected. It is also possible that only one or two fish may get sick, particularly when caught early to prevent the spread of the disease. 

In fact, dropsy in fish is not a contagious disease, the other fish can be infected only in the event of the death of the affected subject. As the infection progresses, skin lesions may appear, the belly fills with fluid and becomes swollen, internal organs are damaged, and eventually the fish die. Even with immediate treatment, the death rate is sadly high. Only fish that are treated in the early stages of infection are able to respond positively to treatment.

Dropsy in Fish

Symptoms of Dropsy in Fish

Symptoms vary from case to case. Some fish have the classic swollen belly, others show skin lesions, while others show no visible symptoms.

This variability is what makes diagnosis difficult. However, in most cases, a range of symptoms, both physical and behavioral, are observed. These include:

  • Belly disproportionately swollen.
  • Swelling of the eyes.
  • Anus red and swollen.
  • White, stringy stools.
  • Ulcers on the body, along the lateral line.
  • Curved vertebral column.
  • Damaged fins.
  • The fish seems lethargic, less active.
  • Or the fish stop eating.
  • The fish often resides on the surface.

These symptoms are the result of the progression of the infection. The internal organs are the first to become infected, especially the liver and kidneys. Anemia occurs which is causing redness of the gills. The abdomen fills with fluid, which is causing the spine to sag. The scales move away from the body, giving the appearance of a pine cone. This symptom is a classic indication that the infection is almost irreversible.

Causes Dropsy In Fish

The bacterial agent that causes dropsy is one of the many negative bacteria commonly found in the aquarium. The underlying cause of a fish becoming infected in the first place is due to the compromised immune system which leaves the fish susceptible to infection. This can happen as the result of stress for a number of factors, such as the following:

  • When the tank is badly managed (hence the importance of siphoning the bottom often).
  • Poor water quality.
  • Ammonia or nitrite peak (it is always advisable to periodically check the values ​​and, if necessary, adjust them).
  • Temperature changes in the tank (a hasty water change can also cause other serious diseases).
  • The stress (the fish can be stressed by several factors: population incompatible equipment not appropriate for the species, too much / little water movement, etc.).
  • Too much leftover food in the aquarium (give the right amount of food to the tenants in the tank without overdoing it).
  • Too aggressive roommates.
  • Other diseases.

In general, a short-lived state of stress will not compromise the immune status of the fish. The lowering of immune defenses due to stress causes is intended for long-term exposure.


With timely diagnosis, it is possible to save infected fish. Treatment is aimed at correcting the problem with supportive therapy for sick fish.

  • Move diseased fish to a quarantine tank.
  • Add the salt to the aforementioned tub, 1 teaspoon for every 3.5 liters.
  • Feed sick fish with high quality food. Possibly fresh.
  • Use a heater by setting the temperature to the same degrees as the main tank.
  • Get a course of antibiotics.

Isolation And Quarantine

It is important to isolate the sick fish in a quarantine tank using the same water as your main aquarium together with an aerator (very important to have one at home, it is often used to treat various fish diseases). In the meantime, do a water change in the main aquarium and monitor healthy fish closely for symptoms appearing in other tenants. Add a tablespoon of salt for every 3.5 liters in the quarantine tank. Keep this tank rigorously clean by performing partial water changes every 3/4 days.

Provide sick fish with a variety of fresh, high-quality foods, but not until the second day. Often this is enough to resolve the infection if it is not too advanced. At the end of the treatment, leave the fish in the tray at least another 2 days to see if it has fully recovered. If everything goes well, you can put it back into the main aquarium. If after 2 days, the fish does not respond well to treatment, you will have to use the antibiotic. A broad spectrum antibiotic specific for bacteria is recommended. It is typically an ambramycin- based drug. The medicine comes in the form of a capsule that must be dissolved one every 20 liters of water. The treatment must last 5 or 10 days. Keep the fish (s) under close observation for several weeks after symptoms have subsided.


As with many diseases, prevention is the best cure. Most of the factors that put fish at risk can be prevented. Since poor water quality is the most common root cause of stress, aquarium maintenance is critical. Other factors to keep in mind are:

  • Perform regular water changes.
  • Keep the aquarium clean.
  • Clean the filter regularly.
  • Avoid overcrowding of the tub.
  • Don’t overfeed.
  • Vary your diet.

If the aquarium is properly maintained, then outbreaks of dropsy are more than unlikely.


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