Dropsy Disease in Fish: Causes, Symptoms, Treatment, and Prevention

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One of the most important aspects of fishkeeping is ensuring the health of your fish, which means keeping them away from diseases. A common one is dropsy in fish, which could catch a new aquarist off guard. This disease may appear suddenly, though there is no need to stress if you know what to expect how to manage it.

Dropsy in fish is caused by a range of factors and can be treated quite easily. It is basically an internal bacterial infection that gives the fish’s body swelling. While this disease is not contagious, it’s often triggered by poor habitat conditions that may have also affected other fish.

If you want to be an expert aquarium owner who can ward off any bad diseases from your fish, you should understand the ins and outs of dropsy. Today, let’s take a look at what it is, the major causes, and how to treat it.

What Is Dropsy?

Before diving into its causes, treatment, and prevention, we ought to explore what dropsy really is. Non-aquarists may not have heard of this disease before as it only ever attacks aquarium fish. Its main sign is swollen bellies, which is why dropsy is often called bloat too.

Symptoms relating to dropsy in fish are induced from a bacterial infection that is often found in home aquarium. Any fish could be exposed to these bacteria, although an unhealthy fish will be more vulnerable and susceptible to dropsy infection. This includes fishes that are stressed or have weaker immune systems.

Symptoms of Dropsy in Fish

Dropsy Bloated Betta Fish

What are some of the most common symptoms of dropsy in an aquarium fish? The good news is that it is usually easy to spot when a fish is infected. Worsening infections may cause fluid-filled bellies that appear swollen, which damages their organs and could cause death.

Unfortunately, the mortality rate of dropsy infection is quite high even with immediate treatment. Only when you diagnose a fish in the very early stages will there be a chance for successful treatment. This could be noticed when they display easy-to-spot swollen belly or skin lesions.

With that said, some infected fishes may show few to no symptoms! Some symptoms are also more behavioral than physical, which means you should be extra attentive and detailed.

Besides swollen belly, some of the physical signs of dropsy in fish are scales that stand out, bulging eyes, pale gills, swollen anus, pale and stringy feces, ulcers, curved spine, clamped fins, as well as red skin or fins.

As a responsible tank owner, we would advise you to always be on the lookout for behavioral symptoms too. This includes watching for general lethargy and refusal to eat. Sometimes, those infected by these bacteria also tend to swim near the surface of the aquarium.

Causes of Dropsy in Freshwater Aquarium Fish

As we have mentioned previously, dropsy is caused by bacterial infection. This bacterium is commonly known as Aeromonas, which can be found in most aquariums and may infect vulnerable fishes. These are those suffering from overcrowding and poor water conditions. Other than that, dropsy in fish may be induced by failing kidney function too.

However, most cases of dropsy are caused by weak immune systems. This is in turn the result of several factors, include:

  • Poor water or living conditions
  • Overcrowding or imbalance tank size vs fish population ratio like we mentioned above
  • Ammonia or nitrite spikes in the water
  • A sudden significant drop in temperature
  • Inadequate nutrition
  • Stress from transportation is also a possible trigger
  • And aggressive tankmates may contribute to a stressful environment for your fish.

Speaking of poor water conditions, there are several practical solutions that can help you a lot to get rid of this problem naturally, including:

  • Add live plants to your tank as they can absorb waste to lowering ammonia and nitrite level
  • Introduce shrimp or another cleanup crew species. You can trust them to finish off leftover food
  • Proper water filters are also very helpful in dealing with the unwanted dirt

Dropsy Treatment and Prevention

dropsy treatment

With that said, there are several alternatives that you can take to cure your fish from dropsy. We will also look at some prevention practices so that the fish can avoid the disease in the first place.

How to Treat Fish With Dropsy

It can be a simple treatment if you know what you are doing. But the most important thing to remember is to isolate the affected fish from other healthy fish. Unfortunately, spotting the disease too late almost always means fatality for the fish, which is why many experts recommend euthanizing. On the other hand, early detection will increase the chance of recovery.

Most treatments for dropsy are focused on addressing the underlying problem and avoiding future infections. It also involves supportive care for the infected fish.

The first step is obvious, which is to isolate the fish infected by dropsy to a quarantine tank. It is advised to keep it empty to make water changes much easier. Make sure the temperature and other conditions are as similar to their original home tank.

Use this to create a “salt bath” by adding a teaspoon of Epsom salt for each gallon of water, although no more than 2.5 teaspoons per ten gallons. This will help draw out any excess water that causes the belly to swell. But be careful not to add too much as a freshwater species will not be able to survive in salty water. Don’t forget to add new salt when performing partial water changes.

In terms of the feeding regimen, our best recommendation is to use antibacterial fish food, which can be store-bought or homemade. Prepare this by mixing high-quality fresh fish food with safe antibiotics such as chloromycetin or tetracycline.

Keep feeding this diet to your fish, in the amount they are used to, for around 8 days. Remember to track and monitor their progress throughout this period while keeping the water condition prime and optimal.

You may see improvements over several days. If not, try treating the water with Maracyn Two. The solution can be absorbed through the skin and help the fish fight against bacterial infection. At this point, you will have done everything you can, so just hope for the best!

Of course, these are just some of the most common home remedies you can provide for the infected fish. There may be other treatments for dropsy in fish which you can get by contacting a local pet store or veterinarian.


Because dropsy in fish is generally difficult to cure once it passes a certain stage, the best thing you can do is to prevent it in the first place. Almost every factor imaginable that could induce stress is preventable. Especially because its most common cause is poor water quality.

This is the root of almost every popular aquarium problem. We cannot stress the importance of tank maintenance enough! This includes everything from regular water changes, having a clean filter, and not overcrowding or overfeeding your fish.

We also advise testing the water conditions in a regular manner and using a gravel vacuum to clean detritus from the tank. Other than that, use flake foods within a month of opening to keep them as fresh as possible. It’s also crucial to vary the diet of your aquarium fish.


All in all, dropsy in fish should be approached just like any other common aquarium fish disease. It is generally difficult to nurse a severely infected fish back to health, although early diagnosis makes this possible. Just make sure to maintain the tank well and keep your fish stress-free!

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