Fishbowl Adviser

Dropsy in Fish: Causes, Symptoms and Treatment

When it comes to making sure your fish are healthy, there are many diseases that pose a risk to them. It is not unusual for new aquarists to be surprised by different conditions that can harm their fish. One of those conditions is dropsy. But what is dropsy and how can you make sure your fish are free from it?

Red betta fish

What Is Dropsy?

Dropsy is often called a disease, but it is an internal bacterial infection that impacts the body of fish and forces them to swell. It is a medical term for a condition that would call edema or ascites nowadays. The condition consists of a number of symptoms that are caused by bacteria that are commonly present in aquariums and causes an infection. It causes the swelling of soft tissues in the fish’s body cavity like the abdomen. Basically, fish get hugely swollen bellies. This happens because of the accumulation of water and any other fluids.

The name for the condition itself comes from the word dropesie in Middle English, hydrops in Old French, and hydrops in Greek, which all translate to water.

Even though dropsy is not contagious, it can cause negative effects for the fish in your tank, as well as the conditions that lead to dropsy. When fish get exposed to the dropsy-causing bacteria, the healthy fish rarely get the disease, but those that have their immune system compromised will have problems. A compromised immune system can happen if the fish experience stress, and if aloof the fish in the aquarium are under stress, the entire tank can get infected.

Symptoms of Dropsy in Aquarium Fish

The symptoms of dropsy can actually vary a lot – from the classic swollen belly to having skin lesions, there’s a variety of symptoms to be aware of. But, although dropsy might not be straightforward, there are a few signs that can help you identify it before it becomes a problem.

The variability of symptoms makes diagnosis difficult, but there are some that can help you identify your fish have dropsy:

  • Bulgy eyes
  • Swollen belly
  • Pale gills
  • Stringy and pale feces
  • Clamped fins
  • Ulcers on the body
  • Curved spine
  • Red and swollen anus
  • Skin redness
  • General lethargy
  • No appetite
  • Swimming near the surface

As this infection progresses, fish can get skin lesions, along with a swollen belly that is filled with fluid, and damaged internal organs, which can ultimately cause the fish to die. Internal organs are affected the most, especially the liver and kidneys. Unless a fish is diagnosed while the infection is in the early stages, successful treatment is highly unlikely. Even if you provide the fish with prompt treatment, the mortality rate is pretty high.

Fish in aquarium

Causes of Dropsy

Dropsy is most commonly the result of a bacterial infection that is caused by a bacteria called Aeromonas. This bacteria can be found in fish tanks, but it won’t affect the fish unless they are stressed, water quality problems, or overcrowded. It is one of the several gram-negative bacteria that can be found in fish tanks.

Once the immune system of the fish is compromised, they can have poor kidney function which can cause water absorption for the body cavity and swelling of the stomach. Dropsy is not contagious, but isolating sick fish from healthy ones will help you easily treat the sick fish before putting them back in the tank.

Some of the things you need to watch and put as part of your regular aquarium maintenance:

  • Poor water quality
  • Water temperature drop
  • Stress in fish
  • Ammonia spikes
  • Nitrite spikes
  • Eating problems and improper nutrition
  • Aggressive fish in the tank
  • Other present diseases


Dropsy is not easily treated and cured. However, if dropsy is detected while it is in the early stages and the sick fish are isolated to get proper treatment, the affected fish can be saved.

The first step is to identify which fish has dropsy and isolate the sick in another tank.  Once the affected fish are quarantined, you can do a water change and watch over the remaining fish closely to see if they have any symptoms.

You should add salt to the tank with quarantine fish – 1 teaspoon per gallon of water. Low salt levels can help with the osmotic balance of the fish by making sure the water salinity in the tank is much closer to the fish’s blood salinity. This will help the fish get rid of any excess water they might have accumulating in the body, which can cause dropsy. But, make sure you don’t add too much salt because it will make the environment unhealthy for freshwater fish.

You should also make sure you feed your fish a healthy diet that consists of quality pellets or flake food, with frozen foods, vegetables, and live foods. Most diseases and problems can be cured with a proper diet or an antibacterial remedy. In addition to a good diet, you can also feed your fish antibiotics that are specifically formulated for gram-negative bacteria, with proper consultation with your veterinarian.


How to Prevent Dropsy

To prevent dropsy and avoid having these problems, you need to monitor the tank from the moment you set everything up. And you need to do regular water testing with a water test kit of your choosing.

The temperature of the tank ideally needs to be between 78 and 80 degrees Fahrenheit. This number can vary, depending on the breed you have. You need to research the exact temperature your fish need to make sure the environment is suitable for your pet. And you need to make sure the filter gets cleaned regularly.

You need to avoid having bad water quality, with no bacteria floating around and compromising the immune system of your fish. The most important thing is to regularly maintain hygiene and react if the tank gets cloudy. And make sure the pH levels in your tank are safe.

Apart from hygiene, regular nutrition is important as well. Do some research on what your fish eat and set up an eating schedule. Make sure you feed your fish properly and make notes if there are any changes in their routine. And don’t overfeed your fish.


  1. Dropsy in Fish – Companion Animals
  2. Goldfish Dropsy Disease – Caring Pets
  3. Dropsy – Excessive Swelling in Fish Due to Kidney Failure – PetMD


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