Dropsy in Koi Fish (Bloating) – Symptoms, Care, Treatment!

Dropsy is an uncommon but dangerous disease that affects a wide range of fish species.

While dropsy has many physical and behavioral symptoms, bloating is the most common.

So, if your koi is bloated or the scales are sticking out, it may be suffering from the dropsy disease.

The good news is that it is fairly common for fish to recover from dropsy if caught early.

Therefore, as a koi owner, you must understand the symptoms, treatments, and science behind the dropsy disease. Read on to learn how dropsy causes bloating in koi and what you can do about it. 

Understanding Dropsy Disease in Koi Fish

Dropsy, often known as Bloater or Pinecone disease, is not really a disease.

It is a bacterial infection caused by a larger health condition that may be difficult to identify at first.

Dropsy attacks Koi fish’s liver and kidneys before shutting them down. It is characterized by the accumulation of fluid within a fish’s body.

Here are the common causes of dropsy in koi.

Poor Water Quality & Injuries

It is often brought on by low water quality. Dirty water might not directly cause dropsy in koi. However, it creates an environment where the disease is far more prevalent.

It is common for germs to infect a sick or injured koi living in such conditions since its immune system has been suppressed.

An infected injury is another common cause of dropsy, and poor water quality is strongly associated with it.

It’s quite likely that an injured koi will get an infection if the water quality is already low.

If the koi were injured and are now bleeding, the water quality may decline further even if the surrounding environment was ideal.

Poor Diet & Malnutrition

If there are no concerns with your water conditions and the koi has no evident wounds, malnutrition may be the cause behind dropsy. 

A koi’s immune system cannot operate properly if it does not receive the nutrition required. Stress can be caused by not feeding your koi enough or providing them with the wrong food.

When this happens, your koi’s immune system weakens, allowing germs to enter. Offer your koi highly nutritious food to ensure a well-balanced diet and a healthy immune system.


If you are certain that you are giving your koi a proper diet, the only likely cause is a parasite.

Flukes may harm your koi, leaving lesions that are hard to detect but provide an ideal breeding ground for germs.

When parasites feed, they harm organs while also siphoning vital nutrients. 

Parasites, unlike dropsy, will transfer from host to host, which means that every koi in the pond is susceptible to dropsy as a symptom.


A crowded aquarium tank or pond can attract various ailments, including dropsy. Overcrowding might cause your koi to get stressed.

This might be due to a lack of adjustment to its new surroundings, food shortage, or bullying from other fish for food.

Too many fish in a pond also allow bacteria like Pseudomonas to reproduce more quickly.

Dropsy might arise as a sign of any sickness due to the excessive amount of germs floating in the water.

Also read: How to Tell if Your Aquarium Has Too Many Fish?

What Are the Symptoms of Dropsy in Koi Fish?

Dropsy is difficult to identify and cure since the symptoms do not appear until the fish has progressed to the terminal stages of the disease.

That’s when the fish physically swells. Its scales protrude, giving the fish the appearance of a pinecone. The trapped fluids may also cause the eyes to protrude out.

However, keep in mind that abdominal swelling is not always a sign of dropsy. Sometimes, when female fish are ripe with eggs or carrying growing embryos, they become rounder noticeably.

Unlike fish affected by dropsy, these females’ scales do not protrude, and they generally appear, eat, and act normally.

Dropsy can sometimes be mistaken for constipation, prevalent in herbivorous fish that are not fed enough green vegetables in captivity.

However, constipated fish have no projecting scales.

Dropsy is frequently associated with external bacterial illnesses such as fin rot, mouth rot, and ulcers. Other common dropsy symptoms include the following:

  • Abdominal swollenness
  • Swelling and bulging eyes
  • Color loss in the gills
  • Fins are clamped together
  • A curvature is forming in the spine
  • Pale or discolored feces
  • Appetite suppression
  • A lack of movement and energy
  • A lack of buoyancy,
  • An inclination to hide

Is Dropsy Contagious?

Is dropsy contagious? Do you need a quarantine tank to treat fish with dropsy? These are common questions inquired by koi owners.

It is true that if one fish in a pond has dropsy, the other will soon follow. However, it is not because dropsy is contagious. Instead, it happens because all fish are exposed to the same water conditions.

Regardless, having a quarantine tank on hand is always a good idea to separate any sick fish. A quarantine tank does not have to be elaborate.

It can even be a temporary structure, such as a stock tank, that can be stored when not in use. Moreover, new fish are also prone to carry contagious diseases.

You must guarantee that this disease does not spread to others.

To avoid this, all new koi should be monitored in a quarantine tank for 14 days to ensure they do not exhibit indications of sickness.

Treatment Options for Dropsy in Koi

Advanced dropsy is difficult to cure, and, in most cases, the koi will not recover.

But if you recognize the symptoms of dropsy early on and take appropriate action, your koi will most likely recover completely.

The first step is determining the most likely reason for your fish’s dropsy. After that, you can take steps to address the problem while the affected koi remain in the quarantine pond.

Re-Evaluate Environmental Conditions

If your water is in bad condition, perform a water change or look into ways to enhance it.

In the meanwhile, start giving your koi adequate food if they are not being provided nutritional food.

If the fish has evident predator wounds but is still functioning normally and eating regularly, the best thing you can do is leave the fish alone.

Continue to feed it and monitor the water conditions, but do not handle or stress the fish. It is also advisable not to administer drugs. Most wounds will heal on their own under excellent water conditions.

In case the wound worsens, or the fish stops eating, treatment may be necessary. In this case, seek the advice of a veterinarian or a specialist.

Consider a Salt Bath

A salt bath increases the salt levels in the pond to be comparable to the koi fish’s internal fluids. It assists the koi fish from drowning.

This should help your koi fish recover from dropsy more quickly. Wounds and illnesses caused by parasites, bacteria, or fungi also respond well to salt baths.

If you don’t want to put salt in the pond, you’ll need to construct a special isolation tank. There should be no more than 5 cups of salt per 100 gallons in the separate tank.

The salt would be more easily dissolved in the water if it were aerated to maintain optimal oxygen levels.

It’s okay to leave your koi fish in the saltwater for up to 10 minutes, but keep an eye out for symptoms of distress.

Also read: Does Aquarium Salt Kill Ich?

Administer Medicine

If addressing the reason does not assist the fish after a few days, or if parasites are the most likely cause, you should try administrating a dropsy medicine to your koi.

Remember that most dropsy treatments are quite harsh and should only be used on infected fish in an appropriate quarantine pond if absolutely required. There are different options you can consider:

Start by treating the water to kill any parasites that may be living in your tank. Once you have gotten rid of all the parasites in the water, you can begin treating the koi fish.

Apply the anti-bacterial medication to get rid of internal and exterior bacterial diseases. As the last step, administer an antibiotic medication to the koi.

Make them Comfortable

If dropsy has severely harmed your koi, there is little hope for them.

At that point, the fish’s essential organs would have been damaged to an unacceptable degree, rendering rescue impossible.

It might become dejected and refuse to swim as much. The stomach may swell and seem bulky. The best you can do is try to keep your koi as comfortable as possible.

Dropsy won’t spread to the other fish in the pond. Even so, a filter should be installed in the pond to improve the water quality.

The micro dust particles and bacteria in the water that form pathogens will be removed with the aid of the activated carbon.

Bottom Line: Prevention Is Better Than Cure

Dropsy is notoriously challenging to cure, which is why prevention is key.

Careful attention to the chemistry and quality of the water, as well as the selection of appropriate meals, is essential for keeping fish successfully.

Refrain from overcrowding the pond. Finally, keep a close eye on your koi to identify any signs of illness as early as possible.

The earlier you detect dropsy, the easier it is to treat!

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