Swollen Fish – Dealing with Dropsy Disease in Your Aquarium

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In this article I will cover a very common problem that fish keepers face. This problem is non-other than the fish dropsy disease. Unlike ich disease, dropsy is harder to treat in fish, so discovering this disease in early stage is crucial.

In the following I will show you what fish dropsy really is and how you can prevent it in your tank, because prevention is the key. Of course, if dropsy is already surfaced, you’ll learn how to treat it as well.

What is Dropsy?

What is Dropsy?

What is Dropsy?

Like I mentioned above, fish dropsy is a common health issue or disease that appears in home aquariums quite often. Another common term for this health issue is bloat. What does it do?

This disease manifests itself most of the time, by affecting your fish’s bellies. How? The belly on an infected fish will drop down, thus the name of the disease. Basically, it refers to a condition in which fish will present large swollen bellies.

There are other symptoms that come with this health problem too, but you’ll learn about them a little later in the article.

Can You Treat Fish Dropsy?

This is probably the most important question that you’re asking yourself regarding dropsy. Unfortunately, the answer is two sided:

On one hand, yes you can treat dropsy. But only with one condition: you have to notice the presence of the disease in its early stages. If you don’t, you have very little chance at treating it successfully (more about this later).

On the other hand, the answer is no, you can’t treat dropsy, if you only notice its presence when it’s too late. We’ll learn about these stages in a moment.

But to treat your fish effectively, you must first know how to notice it in the tank. So, let’s talk a little bit about dropsy causes and symptoms:

Dropsy Disease – Causes and Symptoms

Dropsy Disease - Causes and Symptoms

Dropsy Disease – Causes and Symptoms (sourceCC BY-SA 4.0)

The main cause for dropsy in your tank is a bacteria called Aeromonas. The bad news is that this bacteria can easily appear in any sort of personal fish tank. So, the question is: can your fish be protected from it? Yes they can.

In most cases, only fish that have a compromised immune system will get infected by this bacteria. What leads to such an immune system? Any of the below listed factors:

  • The water quality isn’t good enough
  • Too much ammonia and nitrite in the tank
  • Improper diet
  • A large and sudden drop in the water temperature
  • Other aggressive tank mates
  • Stress that comes with transportation
  • Or even other diseases

Of course, a short exposure to one of these factors won’t compromise your fish so badly, that they’ll  get infected right away. Usually, it takes a longer period for this to happen, or even multiple stress factors that work together in quick succession.

What are some of the other symptoms of dropsy, besides the large swollen belly?

  • Bulging eyes
  • Pale gills
  • The anus of the infected fish becomes red and swollen
  • Ulcers appear on its body
  • The spine becomes curved
  • Fins might clamp together
  • The skin and fins become red
  • The fish refuses to eat
  • It swims near the surface most of the time

These symptoms appear progressively, not all at once. As the disease advances, more and more symptoms appear, giving a clear warning what is happening in your tank.

So, how can you treat dropsy?

Treating Dropsy in Fish

This infection is not easily cured, as I mentioned above. Some experts even say that fish that got infected should be euthanized. This will prevent the spread of the disease in the tank to your other healthy fish.

But what can you do, if the disease was spotted in its early stages? There are some steps you can take, to treat these fish:

  • First of all, move the infected fish to a separate aquarium. In this tank, only keep your sick fish, to make sure dropsy won’t spread all over the others.
  • Something else that helps, is to add salt to the “hospital tank”. Keep in mind this quantity: 1 teaspoon of salt for every gallon of water you have in the infected tank. Be very careful when you add salt. Don’t put too much, because that won’t do any good. Quite the opposite: it will sicken you fish even further, since they don’t react well to it.
  • Only feed these fish with fresh high-quality food. This step is especially important, if you don’t want the disease to strengthen even more.
  • Use antibiotics. You can treat your fish either by mixing it in their food, or adding it directly into the water they swim in.
  • Don’t forget to test the water regularly, every single day, to make sure it’s suitable for your sick fish.

While you do the steps listed above, it’s important to change the water in the original tank as well. This way, you can make sure the disease gets wiped out faster. Also, monitor the original tank too, after you did the water change.

Prevent Fish Dropsy

Prevent Fish Dropsy

Prevent Fish Dropsy

Now, it’s best if this disease never takes place in your tank, right? This is why you must find out what is to be done, in order to prevent dropsy from generating in the aquarium. Here are some good ideas, that already worked for most people:

  • Test the aquarium water regularly, to make sure every parameter is at its normal level. This way, your fish will enjoy a healthy environment.
  • Also, do regular water changes. Even if you keep the parameters at their best, you need to change the water from time to time.
  • Keep the tank clean. Use a quality water filter, that will clean the water from floating debris, and chemical substances that might harm your fish. Also, don’t forget to clean the filter regularly. To ensure a top performance.
  • Don’t overcrowd your tank with too many tank mates.
  • Do not overfeed your fish either.
  • If you feed them flake food, use that within one month after opening the package.
  • Use a variety of foods, not just one single type. This way, you’ll ensure that your fish receive all the nutrients needed to live a healthy life.

If you do all these things I listed right above, you can expect your fish to live happily in the tank, without dropsy ever appearing. Of course, other disease won’t present themselves too easily either, if you maintain the aquarium, like said above.

Don’t forget one thing: do all the steps I described, not just 1 or 2. These steps work together, to result in a healthy tank where fish live long and prosper.

Is Dropsy Contagious to Other Fish?

You probably deduced by now that dropsy really is contagious to other tank mates. After all, that is the whole point why you must separate the infected fish to a quarantine aquarium.

Since the disease happens due to a bacterium, any other fish can get infected, if you keep the sick ones in the tank.

Is Dropsy Painful for Fish?

In most cases yes, dropsy can be quite painful for your fish. That is easily deduced from the symptoms I listed above in the article. How painful?

Well, that depends mostly on the symptoms that appear in your particular case. Some are more painful than others. For instance, having a curved spine and big swollen belly can be quite painful. That is because the internal organs are moved away from their natural place due to the disease, and your fish will feel quite bad during this process.

Is Fish Dropsy Contagious to Humans?

The disease itself is not contagious to humans. However the bacteria that causes the infection can be. It is recommended that you behave carefully when you treat your sick fish. How can the bacteria infect you?

Luckily, it does not spread through the air or just by touching your fish. In most cases, you can get infected through an open wound or by drinking contaminated water. So, be careful about these aspects.

Be especially attentive, if you have children in the house as well. They can get infected easier, duo to their weaker immune system. It’s best to keep the tank with the infected fish out of your children’s reach.

Should You Euthanize Fish with Dropsy?

At first no, you shouldn’t. If you notice the disease in its early stages, there is a real chance for you to treat it effectively. Do everything in your power to help your fish recover from that state.

However, if your fish presents all the symptoms (or most of them) that I mentioned above, there isn’t much of a chance for you to treat them effectively. In this case, euthanizing such fish is the better option.

Just keep in mind that during this sickness, they could be in much pain, and euthanizing them is maybe the best option. But this is up to you to decide in the end.


All in all, as you can see, fish dropsy is truly a common disease that unfortunately results in the fish’s death on many occasions. Because of this, it’s important that you prevent the disease from presenting itself in the tank.

Follow the advice I gave you about this. But if dropsy already made its appearance, do your best to treat it, and get rid of the contaminated environment.

Author Image Fabian
I’m Fabian, aquarium fish breeder and founder of this website. I’ve been keeping fish, since I was a kid. On this blog, I share a lot of information about the aquarium hobby and various fish species that I like. Please leave a comment if you have any question.
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