How to Treat Dropsy in Koi Carp {Treatment & Prevention}

Is your koi carp suffering with dropsy and you are looking how to treat dropsy in koi carp.

Dropsy is actually not a disease, but the fish’s immune response to a bacterial infection that has spread to the vital organs.

Is there anything you can do for your koi carp? Yes there is, I will cover what you need to do below.

How to Treat Dropsy in Koi Carp?

The best way to treat dropsy in koi carp is to add salt to the water and also use an antibacterial treatment which should cure the dropsy infection.

Dropsy in Koi Carp

When a bacterial infection has gotten into the bloodstream of your koi and has been pumped to the vital organs like the kidneys and the liver. This becomes Dropsy, which can cause your fish to become very ill and is usually fatal.

The dropsy is usually caused by a bacterial or fungal infection, because there are two types of infections you will need to apply a few methods to cure this infection.

Will a Salt Bath Help Koi With Dropsy?

Yes. With a salt bath, you are trying to raise the salt levels in a pond to match with the body fluids inside a koi fish. You are helping to not allow too much water to enter the koi fish this way. Your koi fish will hopefully be able to recover from dropsy quicker this way.

Salt bath are used for parasitic, bacterial or fungal infections and wounds. You would have to create a separate isolation tank if you do not want to put salt directly into the pond.

We recommend allowing the separate tank to contain 5 cups of salt per 100 gallons. Aeration would help to dissolve the salt into the water and keep oxygen levels ideal. Your koi fish can remain in the salt bath for up to 5 to 10 minutes, but look closely for any signs of stress.

Signs Your Koi Carp Have Dropsy

Dropsy creates swelling. You may notice that your koi fish is showing the following signs:

  • Bulging eyes
  • Swelling in the body
  • Loss of buoyancy
  • Darling of color
  • Excessive hiding
  • Sulking in the corner

Thankfully, dropsy is not contagious between koi fish. Just because one of your koi fish is affected with dropsy doesn’t mean that the entire pond life is at risk.

You should be able to isolate this one particular koi fish with dropsy and try to apply a broad-spectrum antibiotic treatment to help cure it. If dropsy has reached an advanced age, it may not be possible to cure.

What Causes Dropsy in Koi?

Dropsy can be caused by an improper diet, addition of new parasites into the pond or simply overstocking it with too many pond mates.

The water quality gets poor when there are too many additional parasites, bacteria and pond life living in the same space with your koi fish. It can become hard to manage and bacteria will end up thriving in such a condition.

This environment can weaken the immune system of your koi fish. The bacteria inside the pond infects your koi fish when its metabolism slows down.

Two types of bacteria known as Pseudomonas and Aeromonas are not as dangerous when your koi fish is at optimal health. When water quality is reduced,  or stress levels are raised, these bacteria can have a contributing factor to developing dropsy.

How to Treat Dropsy in Pond Koi

A couple of go to methods for healing wounds and dropsy are broad-spectrum antibiotics and a product such as Melafix.

At this point you will have to offer the most nutritious food available. Your koi fish would prefer to swimming in water with plenty of dissolved oxygen. An air pump would help as well.

There are combinations of special medicines available. You may need to visit your local fish shop and ask them about what they have available to treat dropsy.

The advanced stages of dropsy makes it impossible for it to be cured. At this point you will have to keep your koi fish comfortable. It may want to sulk in the corner and not swim as much. The belly may become thick and bulging.

Thankfully this koi fish is not going to spread the disease to other fish in the pond because dropsy is not contagious.

Nevertheless, it’s a good idea to place a filter into the pond to increase the water quality. The activated carbon will help to purify the water further and get rid of some of the micro dust particles and bacteria within that are creating pathogens which encourage the development of dropsy.

How Do You Treat Dropsy In Koi?

Dropsy can be fatal by the time you spot the most obvious signs. So you need to act asap if you spot dropsy in your koi fish.  The exceptions to this, however, is if the Dropsy has been caused by a mild fluid retention problem or if the parasitic infection that causes severe dropsy is in its earliest stages.

To treat dropsy in koi fish do the following

  1. Add Aquarium Salt To The Water
  2. Apply Anti-Parasite Treatment
  3. Apply External Anti-Bacteria Treatment
  4. Apply Internal Anti-biotic Treatment

More information on the above

1. Add Aquarium Salt To The Water

By adding aquarium salt (Available to buy on Amazon) to the water this will help to kalm your koi and reduce any stress they might be suffering with.

It will also close any open wounds that the koi might have which will reduce the risk of further infection.

2. Apply Anti-Parasite Treatment

The next thing we need to do is treat the water and kill any parasites that might exist in your tank, You can do this by adding anti-parasite treatments (Available to buy on Amazon) to the water, Personally I have always used the Blagdon anti-parasite treatments and have very good results every time.

3. Apply External Anti-Bacteria Treatment

Now we have removed all the parasites from the water we can start to treat the koi fish, We will need to use two types of anti-bacterial treatment for treating internal and external bacterial infections.

For an external anti-bacterial treatment I recommend to use Melafix

4. Apply Internal Anti-biotic Treatment

The last thing we need to do is to give the KOI an anti-biotic treatment which will give them the best chance of survival.

How To Treat A Koi Fish With Advanced Dropsy

Unfortunately, there’s no way to save your koi, once they’ve been seriously affected by parasitic-caused Dropsy. By that time, there has been too much damage done to the vital organs and the fish will not be able to be saved.

When mild dropsy symptoms are spotted, if there’s no presence of infection or any parasitical problem, you may have a chance to treat it. This is when the Dropsy has been caused by your fish’s problem retaining proper fluids to say alive, which can be treated by adding salt to the water.

If you do spot the parasitic infection that causes the fatal kind of dropsy in it’s early stages, you can use treatments like Acriflavine or Potassium Permanganate baths. These can be found at your local pond supply store.

How Do You Treat Fungus On A Koi Carp?

There are many different signs of a fungus infection in koi, including the mold-like patches, coming to the surface for air, and sores on the scales of the fish. Luckily, you can usually treat this with a number of solutions that can be found at any aquatic store.

You can detect fungus on your koi, as it looks quite similar to regular mold starting to grow. These spots or patches of your koi’s body will look like a white cotton puff growing on it’s scales.

The first thing you want to do is quarantine the infected koi, unless you know all of them have a fungus. This will ensure that it wont spread to anymore of them. Hopefully, you’ll stop the problem before it goes further.

Most pond treatments for fungus of this sort are actually very dangerous to your koi. The chemical burn the gills, lungs, and other organs, while it’s trying to burn off the mold off the affected areas.

This can be extremely harmful to your fish and really isn’t a great solution. Fortunately for you, there are much better options.

Here are some nonaggressive options for you to treat fungus on your koi fish.

  • A saltwater bath with aquarium freshwater salt.
  • Hydrogen peroxide treatment on infected patches.
  • Formalin and Malachite Green solution cream for fungus spots.
  • Medicated food to target the problem from the inside. (Available at most pet stores)

Is Dropsy In Koi Contagious?

Dropsy is not contagious, but the cause of the dropsy is. The most probable cause for dropsy in your koi is a parasitic infection, which is very contagious and dangerous to the health of your pond.

Usually, dropsy is caused by parasites, which then cause infections to the sores they create. The dropsy is only a result of the already spread infection, which is why it’s usually untreatable once it’s at that stage.

However, the parasites that have started this whole problem are highly contagious. Once the infected fish isn’t provided enough, the parasites will then search for a new host, meaning your other fish.

The bacteria that causes the infection may also be contagious to fish that are mildly affected by parasites, which then leads them to become more ill. Additionally, the parasites and bacteria won’t just attack your fish, but all life in the pond.

Should You Feed A Koi With Dropsy

You can feed a dropsy-infected fish, but the most likely outcome is that it won’t eat. When dropsy symptoms start to occur, the vital organs are shutting down, so fish is likely too sick to eat.

In the early stages, you can treat initial illness by feeding them medicated food. At the stage of dropsy symptom development, the kidneys and liver are shutting down, and one of the main signs is lack of appetite. In fact, it’s usually the first sign that something is wrong.

If you feed anything to a dropsy-infected koi, it should be medicated pellets or antibiotics. On the off chance that the dropsy has been caused by a water retention issue, then you can continue to feed it as normal.

However, feeding a fish that won’t eat will only attract more of the bacteria that caused the infection that started the whole process. The wasted food will only rot and cause a bigger problem in the end.

How To Prevent Dropsy In Koi Fish

Keeping your pond full of fresh, clean water, free of parasites can be a bit of a task. Parasites are everywhere, and once your fish have them, it’s even harder to treat than it is to prevent them in the first place.

  • Here are some tips to keep your koi pond free of dropsy-causing parasites.
  • Changing the water on a regular basis.
  • Regular water quality tests.
  • Keeping a clean pond liner. Checking regularly for buildup.
  • Resisting the urge to overfeed your fish
  • Always having a clean filter
  • Having beneficial bacteria to improve the negative vs positive bacteria balance of your pond.

As a side note if your there’s a lack of sodium in the water, your fish may come down with dropsy from too much fluid retention. Like we said, this can be easily treated by adding salt to the water.


Hello, I'm Jason. I'm the guy behind I volunteer at my local fish shop and I created this site to offer tips and advice on the fish I care for.