Hepper is reader-supported. When you buy via links on our site, we may earn an affiliate commission at no cost to you. Learn more.

What Causes Dropsy In Fish: Symptoms, Causes & Prevention

Lindsey Stanton Profile Picture

By Lindsey Stanton

dropsy in white betta fish

Something that needs to be said about dropsy for fish is that it is usually classified as being a symptom of other diseases or conditions, not a disease of its own.

Dropsy is usually the result of a bacterial infection, from bacteria that are usually present in the aquarium at all times.

Generally speaking, poor water quality and stress lead to a weakened immune system, which then allows those harmful bacteria to infect the fish.

divider fish plants 2What Is Dropsy in Fish?

What is important to note is that, once again, dropsy, although it can be categorized as its disease or condition that affects freshwater fish, it only occurs when several factors come together. Once again, many fish diseases like this are caused by bacteria that are always present in the aquarium.

Dropsy is characterized by the swelling of the fish, particularly the body cavity. The reason why it is called dropsy is that the bellies of fish will swell and drop down, like a potbelly pig.

In this case, dropsy is caused by Aeromonas, a bacteria that is often present in most, if not all fish tanks. Now, most fish living in good water, with healthy immune systems, are immune to these bacteria. This is a disease that mostly affects tropical fish.

However, there are various factors, such as poor water quality, infrequent water changes, stress, and other factors, which can weaken the immune system of your fish, thus making them susceptible to infection from the dropsy bacteria.

For those of you worrying about dropsy being contagious from one fish to another, don’t worry because it is not contagious. However, if there are various factors in the tank causing dropsy in your fish, chances are that the other fish in the tank may develop it as well.

bloated dropsy goldfish
Image Credit: Wari_Nuchczy, Shutterstock

Symptoms of Dropsy

One of the keys here is to detect dropsy in fish in its early stages. The more you allow fish dropsy to develop, the worse it will get and the harder it will be to treat it.

There are various symptoms that fish with dropsy will display. Let’s take a quick look at the various symptoms that a dropsy fish may display. Here is a complete list.

  • Extremely swollen belly
  • scales that stand out from the body like pinecones
  • Bulging eyes
  • Very pale gills
  • Red and swollen anus
  • Pale and stringy feces
  • Ulcers on the body, particularly along the lateral line
  • A curved spine
  • Fins clamped together
  • Red skin and/or red fins
  • General lethargy
  • A refusal to eat
  • Swimming near the surface

If your dish is displaying any of these symptoms (especially ones such as raised scales and pale gills), then you need to act immediately to remedy the situation, as dropsy in fish, when left untreated, is often fatal.

Causes of Dropsy

The most important thing to know here is that fish dropsy, although it is caused by specific bacteria that are usually present in many aquariums, those bacteria won’t be able to infect your fish if it has a healthy immune system.

That said, many things can decrease your fish’s immunity to diseases like this. Infected fish with this disease are usually subjected to stress, poor water quality, bad parameters, and more.

So, what are the main causes of dropsy in your aquarium fish? Simply put, stress can cause poor immunity, and stress can be caused by several things.

dirty water
Image Credit: Chaikom, Shutterstock

Poor Water Quality

One of the main causes of stress in fish, which can lead to this disease taking hold, is poor water conditions If your fish tank contains too much ammonia, nitrates, or nitrites, it can cause these bacteria to take hold in your aquarium inhabitants (we have covered a separate article on lowering ammonia levels which you can find here).

Poor conditions and high ammonia levels are usually caused by inadequate filtration. Maybe your filter is not strong enough, maybe it is broken, or maybe you have not cleaned it enough.

Bad water conditions can also be caused by not performing water changes as frequently as you should. Overfeeding your fish may also cause poor water conditions.

Bad Water Parameters

Aquarium fish require specific parameters, and this generally refers to water temperature, pH level (acidity), and hardness (dGh).

Every aquarium fish needs the temperature, pH, and hardness to be at a certain level. If any of these parameters are off, especially by a lot, and especially for a long period, it can easily cause stress in fish, which can then lead to dropsy development.

Goldfish swimming in an aquarium that looks algae filled and with cloudy water
Image Credit: Chaikom, Shutterstock


If you just bought a new fish and brought it home, it may be stressed out due to improper transportation. Be sure to transport your fish properly, and acclimatize it to the new fish tank the right way to prevent transportation stress from occurring.

Sick fish can be sick due to nothing more than stress, and then, with bacteria thrown into the mix, things can get ugly real fast.

Improper Feeding

Aquarium fish also need proper nutrition. Some fish are herbivores, other carnivores, and most are omnivores.

If you have not been feeding your fish the diet it needs, with the right levels of proteins, fats, vitamins, and other nutrients, it can easily lead to a sick fish, and not just from dropsy.

Image Credit: Image Credit: Peter Dakomd, Pixabay

Aggressive Tank Mates

Aggressive tankmates may also cause stress in your fish, which can then lead to the development of disease.

Fish that are being bullied and constantly harassed often have weak immune systems, which then makes them susceptible to various fish diseases.

Other Diseases

Of course, fish that are suffering from other diseases already have compromised immunity, thus creating the perfect storm for the Aeromonas to take hold of your fish.

Dropsy Treatment

Image Credit: BannokStock359, Shutterstock

There are several treatment options at your disposal to treat infected fish. Once again, this is a serious condition and it requires immediate attention.

Failure to act can quickly result in the death of your aquarium inhabitants. Here is a list of the best treatment options.

  • Immediately move the fish to a hospital tank. Make sure that the hospital tank has a great filter to maintain pristine and clean water, and make sure that the parameters are ideal for the fish in question (temperature, pH, hardness).
  • In the hospital tank, add 1 teaspoon of salt for each gallon of water. The bacteria that causes dropsy is susceptible to salt, and salt does make for a great disinfectant.
  • Ensure that you are feeding your fish only the highest quality of foods that meet and exceed its nutritional requirements.
  • You should purchase antibiotics that are designed to treat dropsy. These may be food-based antibiotics or you may find a medicine that can be added right into the aquarium.

How To Prevent Dropsy

Image Credit: hedgehog94, Shutterstock

Quite honestly, dropsy in aquarium fish can be quite hard to treat, with treatments often being unsuccessful. Therefore, the best thing that you can do for your fish is to prevent this horrible condition from taking hold in the first place.

Here are all of the steps you can take to prevent dropsy from taking hold of your fish.

  • A regular water change is called for. To keep the tank as clean as can be, a 30% water change per week is called for.
  • On that same note, be sure to clean the tank every week, and ensure that you remove all dying plant matter, fish waste, and uneaten food. Using a gravel vacuum will come in handy here.
  • Make sure that your tank has a filter that can easily process the entirety of the tank several times per hour. Also, make sure that the filter features top-notch mechanical, biological, and chemical filtration. You also want to make sure to clean the filter regularly. Simply put, keep your aquarium water clean.
  • When transporting your fish and putting it in a new aquarium, always make sure to follow proper transportation and acclimatization procedures.
  • Always feed your fish high-quality food that meets or even exceeds its dietary requirements. Don’t overfeed your fish either, as uneaten food will rot in the tank, affecting conditions.
  • Never house your fish in aquariums with tank mates that are not ideal. Larger and more aggressive fish may bully the smaller and slower ones, thus causing stress that can lead to dropsy.

divider fish plants 2Conclusion

The bottom line is that if you take good care of your fish, you keep the tank clean, feed the fish right, and don’t house it with tank mates that may cause stress, then dropsy should not be a problem.

However, if you do notice that your fish has dropsy, you need to take immediate action, or else the condition will most likely prove to be fatal.

Feature Image Credit: Dmytro Sheremeta, Shutterstock

Related Articles

Further Reading

Vet Articles

Latest Vet Answers

The latest veterinarians' answers to questions from our database