Aquarium Fish Diseases

Dropsy in fish: guide on symptoms and treatment

Keeping your tank healthy is the number one priority for aquarists. So if a fish develops dropsy, that’s a problem you have to deal with.

But many aquarists don’t know where to start when it comes to dropsy. The causes, symptoms and treatment are a mystery!

That’s why we put together this resource. It will teach you everything you need to know about dropsy in fish and how to get it out of your tank.

Let us begin.

What is dropsy?

Before we get into the nitty-gritty details, we need to start with a quick explanation of what dropsy is.

Simply put, dropsy is a condition that presents as swelling or swelling in fish. It can affect the vast majority of species (including bettas and all types of goldfish) kept in aquariums, and has a number of different possible causes.

If you have goldfish, we recommend reading our post dedicated to hydrops in goldfish.

This swelling is usually isolated to the abdomen (belly) of the affected fish. It can become quite pronounced depending on the severity.

While some homeowners mistake it for a cosmetic issue, it’s much more serious than that. Dropsy is usually fatal.

Author’s Note: It is worth noting that dropsy is a condition and not technically a disease. This is a common misconception that has led to a lot of misinformation over the years.

Is Dropsy contagious?

For the most part, dropsy is not usually contagious. However, you’ll assume it’s out of an abundance of caution when providing treatment (more on this later).


There are a number of common and obvious dropsy symptoms that you should be aware of. However, there is one that stands out the most:


A fish that is severely affected by this condition will have swelling primarily in the abdomen (although this is not always the case). This is caused by a buildup of fluid in the tissue.

If things have gotten to the point where there is significant swelling in the abdomen, then the outlook is not very good. That means things have progressed to the point where it’s affecting your entire body (ie your organs).

Fortunately, there are other symptoms to watch out for that often occur before things get this bad. Your fish may be developing dropsy if it has:

  • Eyes that begin to swell and bulge.
  • Scales that start to point outward instead of being flush with your body
  • A loss of color in their gills.
  • Fin Attachment
  • A curve that develops in your spine.
  • pale stools
  • Swelling near your anus
  • loss of appetite
  • Lack of energy and movement.

If you are regularly observing your fish, then any of these symptoms should really stand out. Once you see something that worries you, it’s best to act immediately before the condition progresses further.


There are many causes of dropsy that you should be aware of. While we’ll discuss specific treatments and prevention a bit later, understanding the causes of this condition will help with that as well.

Scientifically, the main cause of the actual symptoms is a type of bacteria called Aeromonas. Contrary to what some people think, this bacteria is present in your tank at all times. It is not a foreign invader that comes in and wreaks havoc on your aquarium.

Only when a fish has a weakened immune system does the bacteria become a problem.

This means that you should not think of bacteria as the cause of dropsy. The real cause is what compromised your fish’s immune system in the first place.

Here are the usual culprits:

  • poor water quality
  • Inconsistent water temperature
  • Nitrite and ammonia fluctuations
  • poor diet

The good thing about all of them is that you can control them completely. If you can maintain a healthy and optimal habitat for your fish, these problems are unlikely to arise.

Dropsy Treatment

We know that many aquarists want to learn how to cure dropsy. Unfortunately, that is not possible. There is no quick and easy cure that will make this condition magically go away.

Instead, you will need to follow a multi-step treatment process. Results will vary depending on the severity of the dropsy case, but you will give your fish the best chance possible.

quick in quarantine

The first and foremost thing you can do when trying to treat dropsy is to quarantine affected fish. This means a completely separate tank that has the necessary water parameters for any species you suspect may be sick.

It is best to keep this tank bare and devoid of decorations. Even if your fish normally prefers plants, rocks, and driftwood, you don’t want to add any variables to your tank. A filter and a heater will suffice.

Once you have the quarantine tank ready to go, move the affected fish.

Author’s Note: Although dropsy is not normally contagious, removing diseased fish allows you to provide better direct treatment without affecting others.

Add a little salt

Now that the affected fish has been isolated, it is time to add some salt to the tank. The general rule of thumb to follow is 1 teaspoon for every gallon of water in the tank.

Salt is helpful in treating dropsy because it can draw out some of the water and fluid that accumulates in the body. This will help make your fish more comfortable and put them in a better position to recover (uncontrolled bloating is always fatal).

There are many different salt products you can use, but we only recommend one brand. Even if you don’t have a dropsy fish right now, we think it’s a good idea to have some of these on hand just in case:

Step up your diet

While providing the perfect diet is always something you should strive for, it is absolutely necessary when treating dropsy.

Here’s an example we like:

Imagine if you were trying to fight off a serious illness while only eating cereal for every meal. You don’t need to be a nutritionist to know that this won’t end well!

High-quality food will not only provide essential nutrients and vitamins to aid the healing process, but will also help your fish strengthen its immune system.

The perfect diet will obviously vary depending on the species you are treating. We recommend reading a detailed guide on caring for your fish if you are not sure what foods to prepare.

use antibiotics

The last option for the treatment of dropsy is a reliable antibacterial drug. Depending on the level of severity and how well your fish responds to the other treatment methods, you may not need to go down this route.

However, if your symptoms don’t improve, antibiotics are the next step.

It is very easy to apply the medication to your tank. All you need to do is follow the instructions on any product you buy.

But choosing the right product is very important. There are many of them on the market and they all claim to offer the same benefits.

Fortunately, we can recommend the best. The antibiotic below has been used by countless aquarists to help treat dropsy and other ailments. We also personally know many happy users.

Obviously, there are no guarantees when it comes to medication (as you know, there is no cure for dropsy), but this antibiotic will give you the best chance.

How to prevent it

If you read the section of this guide on the causes of dropsy, you can probably guess which methods are most effective in preventing it.

Maintaining excellent water quality and a healthy tank will drastically reduce the chance of your fish developing dropsy. Almost all the factors that cause this condition stem from suboptimal living conditions.

First, take water quality seriously. You need to be consistent with basic water parameters and ensure that nitrite and ammonia levels are stable.

You should always strive for clean, healthy water by using proper filtration, performing water changes, and not adding unnecessary organic waste by overfeeding.

Author’s Note: To monitor these levels, you should regularly test your aquarium water to make sure nothing goes unnoticed. You can avoid many problems just by being informed and reacting quickly.

Second, don’t get lazy about your diet. A healthy and balanced diet will make your fish healthier in general and more resistant to disease.

Go the extra mile to provide some variety and try to feed your fish the highest quality food you can find. Putting in some extra time now will prevent headaches and heartache in the future.

Lastly, do your best to minimize stress on the tank. Fish that live in a state of constant stress are at a much higher risk of developing disease and illness. Keep your fish in a stable aquarium that meets their needs and they will be very happy.


Dealing with dropsy is something no hobbyist wants to deal with. But sadly, it’s part of the hobby.

That’s why it’s smart to educate yourself about this condition and what your options are. By learning more, you’ll be prepared if one of your fish is unlucky enough to land you.

The good thing is simply staying committed to maintaining optimal habitat, it will probably never happen! Go the extra mile for your fish and they will live a long and healthy life.

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