Dropsy In Fish: Your Guide To Symptoms & Treatment

Keeping your tank healthy is priority number one of you’re an aquarist. So if a fish develops dropsy, that’s a problem you need to deal with.

But many fishkeepers don’t know where to start when it comes to dropsy. The causes, symptoms, and treatment are all 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 you can it out of your tank.

Let’s get started.

What Is Dropsy?

Before we jump into the nitty-gritty details, we should start with a quick explanation of what dropsy is.

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

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

While some owners mistake it for a cosmetic issue, it’s far more serious than that. Dropsy is often fatal.

Author Note: It’s worth pointing out that dropsy is a condition and not technically a disease. This is a common mistake that has led to a fair amount of misinformation over the years.

Is Dropsy Contagious?

For the most part, dropsy is usually not contagious. However, you will be assuming it is for the sake of caution when providing treatment (more on this later).


There are a number of common and obvious dropsy symptoms for you to look out for. However, there is one that stands out the most:


A fish that’s seriously affected by this condition will exhibit swelling primarily in their abdomen (although this isn’t always the case). This is caused by a buildup of fluid in the tissue.

A goldfish with dropsy

If things have gotten to the point where there is significant swelling in their belly then the outlook is not great. That means things have progressed to the point where it’s affecting their entire body (namely their organs).

Fortunately, there are other symptoms you can keep an eye out for that will typically occur before things get this bad. Your fish might be developing dropsy if they have:

  • Eyes that are beginning to swell and bulge
  • Scales that starting to point outward instead of lying flush with their body
  • A loss of color in their gills
  • Clamping of the fins
  • A curve developing in their spine
  • Pale feces
  • Swelling near their anus
  • A loss of appetite
  • A lack of energy and movement

If you’re regularly observing your fish then any of these symptoms should really stand out. Once you see something that concerns you it’s best to take action immediately before the condition progresses any further.


There are many causes of dropsy that you should know about. While we will get into specific treatments and prevention a bit later on, understanding what causes this condition will help with that too.

Scientifically, the root 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’s not some foreign invader that comes in and wreaks havoc on your aquarium.

It’s only when a fish has a weakened immune system that the bacteria becomes a problem.

This means you shouldn’t think of the bacteria as the cause of dropsy. The real cause is whatever compromised the immune system of your fish in the first place.

Here are the usual culprits:

  • Poor water quality
  • Inconsistent water temperature
  • Fluctuations in Nitrite and Ammonia
  • Poor diet

The good thing about all of these is they’re completely controllable by you. If you’re able to maintain a healthy and optimal habitat for your fish, it’s unlikely that these issues will come up.

Dropsy Treatment

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

Instead, you’ll need to follow a multi-step treatment process. Results will vary depending on how severe the case of dropsy is, but you’ll be giving your fish the best chance possible.

Quarantine Fast

The first and most important thing you can do when trying to treat dropsy is setting up a quarantine for the affected fish. This means a completely separate tank that has the necessary water parameters for whatever species you suspect might be sick.

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

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

Author Note: Even though dropsy isn’t normally contagious, removing the sick fish allows you to provide better direct treatment without affecting others.

Add Some Salt

Now that the affected fish has been isolated it’s time to add a bit of salt to the tank. The general rule of thumb to follow is 1 teaspoon for each gallon of water in the tank.

Salt is helpful for treating dropsy because it can pull out some of that water and fluid that’s built up in their body. This will help make your fish more comfortable and put them in a better position to recover (unchecked swelling is always fatal).

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

API Aquarium Salt For Health And Disease Recovery

  • Promotes fish health and disease recovery with increased electrolytes
  • Improves respiration for fish in freshwater aquariums
  • Effective solution for treating dropsy
  • Made from evaporated sea water for all-natural results

Step Up Their Diet

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

Here’s an example we like:

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

High-quality foods will not only provide essential nutrients and vitamins to aid the healing process, but it will help your fish build their immune system back up as well.

The perfect diet will obviously vary depending on the species you’re treating. We recommend reading an in-depth care guide about your fish if you’re not sure what foods to prepare.

Use Antibiotics

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

However, if their symptoms aren’t improving then antibiotics are the next step.

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

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

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

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

API MELAFIX Medication

  • Heals bacterial infections, treats dropsy, and repairs damaged fins and open wounds
  • Contains natural, botanical tea tree extract to quickly and rapidly help fish
  • Also helps treat newly-introduced fish to reduce risk of disease outbreak in freshwater aquariums
  • Use daily for a week when treating infections and for 3 days as a preventive when adding new fish

How To Prevent It

If you read the section of this guide about what causes dropsy, you can probably guess what methods are most effective for preventing it.

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

First, take the water quality very seriously. You should maintain consistency with the core water parameters and make sure Nitrite and Ammonia levels are stable.

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

Author Note: In order to keep an eye on these levels you should regularly test the water in your aquarium to make sure nothing goes unnoticed. You can prevent a lot of problems simply by being informed and reacting quickly.

Secondly, don’t get lazy with their diet. A healthy and balanced diet will make your fish healthier overall, and more resilient to sickness.

Go the extra mile to provide some variety and try to feed your fish the highest-quality food you can find. Spending some extra time now will prevent headaches and suffering later. 

Lastly, do whatever you can to minimize stress in the tank. Fish that live in a constant state of stress are at a much greater risk of developing disease and illnesses. Keep your fish in a stable aquarium that meets their needs, and they’ll be quite happy.


Dealing with dropsy is something no aquarist wants to deal with. But unfortunately, it’s a part of the hobby.

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

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

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