Why is my Goldfish Swollen?

Written By Lewis German  |  Disease  |  0 Comments

Goldfish are popular pets, especially with kids. These beautiful fish come in myriad shapes and colours, are relatively straightforward to care for, and are hardy.

However, these lovely fish can sometimes suffer from health problems, including swellings. 

This article discusses some of the most common causes of swellings that might affect your pet goldfish, including how to treat and prevent the problems. So, be sure to keep reading to learn how to protect your fishy friend!

How do you know if your goldfish is swollen?

There are a few telltale signs that can indicate your goldfish is swollen – the most obvious of these signs is that your pet has a much larger belly than usual. However, that can sometimes be tricky to spot, especially if you have one of the round-bodied varieties of goldfish. 

You might notice your goldfish is struggling to swim on an even keel, is floating at the water’s surface unable to descend, or is stuck on the bottom of the tank. Your pet could also appear lethargic and stop eating, and his scales might look raised, like a pinecone.

Common causes of goldfish looking swollen

There are several reasons why your goldfish might appear swollen, some being more serious than others. To treat your pet successfully, you’ll need to know what’s causing the swelling, and this section of our guide will help you do that.

Goldfish with a swollen stomach

A swollen stomach can be a sign of various health problems in goldfish, including the following:


One of the most common causes of a swollen stomach in goldfish is overfeeding. If your fish eats more food than it can digest, digestive problems and bloating will commonly result.


Goldfish, especially round-bodied fancy varieties, often suffer from constipation. That often happens if you feed your fish too much dry food. The food backs up in the fish’s digestive tract, causing the belly to swell and become distended.

Over my 40 years of fish keeping, I’ve learned that including a portion of live food, frozen meaty protein, or fresh veggies in your pet’s daily diet can effectively prevent digestive issues like constipation and bloating. 

However, it’s still essential that you don’t overfeed your fish, so offer only what they will clear in a minute or two and feed them twice daily.

Internal parasites

Parasites, including nematodes and tapeworms, can lead to a swollen abdomen. That’s because internal parasites can interfere with the goldfish’s digestive system and absorption of nutrients. 

Swim bladder disorder

Swim bladder issues will cause buoyancy problems and a swollen belly. However, avoiding overfeeding can help to prevent swim bladder disorders, although gulping air and bacterial infections can also be to blame.


Dropsy causes swelling of the entire fish due to fluid retention and is discussed in more detail below.

Egg binding

If you have a female goldfish, she might develop a swollen belly if she cannot expel her eggs properly. This condition, known as egg binding, might require intervention.

Tumours or growths

Sometimes, tumours or growths can develop in the fish’s abdomen, causing swelling. These lumps can be benign or malignant. In some cases, the tumour doesn’t cause any problems other than making the fish appear fat. However, if a tumour is cancerous or presses on one of the fish’s vital organs, the prognosis is not positive.

Goldfish with a swollen eye

Goldfish can be prone to suffering from swollen eyes. Again, that condition has various causes, including those outlined below.

Of course, goldfish varieties, such as bubble and telescope eye fish, naturally have protruding eyes and should not be confused with sick fish!

Bacterial infections

Bacterial infections, including those caused by Pseudomonas or Aeromonas bacteria, can cause swelling around the eyes of fish. Those infections often occur due to stress or poor water quality that compromises the fish’s immune system.

Parasitic infections

Sometimes, external parasites can irritate and inflame the fish’s eyes, leading to swelling.

Fungal infections

Fungal infections can attack the goldfish’s skin and eyes, causing swelling. These infections often set in when the fish is stressed or when the tank water is high in nitrates.

Trauma or injury

Round-bodied goldfish are clumsy swimmers, typically bumping into things in the tank and often sustaining injuries that can result in swelling.


Popeye is medically known as exophthalmia. In this condition, the fish’s eye swells and bulges out from its socket, sometimes appearing cloudy. If left untreated, the condition can result in a lost eye or damaged vision, although it is usually treatable, depending on the cause.

Popeye is usually caused by infection, injury and poor water quality.

Goldfish with swollen lips

There are two main causes of swollen lips in goldfish. It’s possible that the fish has something, like a piece of gravel, stuck in its mouth that makes it appear swollen. 

Alternatively, the fish could be suffering from a bacterial infection. Any red marks around the fish’s mouth are most likely due to poor water quality.

Does Dropsy make goldfish look swollen?

Dropsy can make your goldfish appear swollen, puffy and bloated. In fact, your unfortunate pet can look like he’s about to explode if he’s suffering from this condition.

What is Dropsy?

Dropsy is not actually a disease but a condition caused by multiple pathologies. 

Goldfish with Dropsy generally have gills and or kidneys that are not working correctly. Many fish issues, including viruses, cancer, bacterial infections, diet and poor water quality can cause that.

When the goldfish’s kidneys don’t work properly, its body can’t remove waste products and maintain the body’s pressure with the environment around it. When kidney function deteriorates, excess fluid accumulates in the body, causing it to swell and appear bloated.

What are the symptoms of Dropsy in goldfish?

There are four main symptoms to look for that can indicate your goldfish is suffering from Dropsy.

Extremely swollen abdomen

A bloated, swollen abdomen is a clear indication that your goldfish might have Dropsy.

Scales standing out

Fish with Dropsy often exhibit pine coning. That means the fish’s scales stand up like those on a pine cone. When the fish’s body is swollen, its scales are loosely attached and not packed tightly as they are in healthy fish.

Bulging eyes

If one or both of your goldfish’s eyes are bulging out, that can be a sign of Dropsy. However, bug eyes can also be symptomatic of a condition called Popeye, as described earlier in this article.

Swimming difficulty

One of the most common signs of Dropsy in fish is that it will have extreme difficulty swimming. The fish might float to the water’s surface, sink to the bottom, or even get stuck on one side. That’s because of the internal swelling caused by fluid accumulation, which displaces the fish’s swim bladder, preventing it from working properly.

Fish upside down

Colour loss

Goldfish are renowned for their brilliant, dazzling colours. However, a goldfish with Dropsy will have faded, lacklustre coloration that lacks sparkle.

Flaccid dorsal fin

In a fish affected by dropsy, the dorsal fin will droop and appear flaccid. You might also notice bloody streaks and blotches on your pet’s other fins.

Gill inflammation

Healthy goldfish keep their gills clasped to their heads except when they are breathing deeply, which they do periodically. However, in a sick fish, the gills will be inflamed or partially closed.

Swollen tail

In goldfish with Dropsy, their tails often swell and become very fat. 

What causes Dropsy?

There are numerous infectious agents responsible for causing Dropsy in goldfish, including the following:

  • Aeromonas spp
  • Myxobolus spp
  • Microcystic Viridis
  • Cyprinid herpesvirus-2

Certain parasites, including Hoierelluscarassii and Mycotic Granulomatosis, can also be responsible for causing Dropsy in goldfish.

Treatment of Dropsy in goldfish

The prognosis for a goldfish with Dropsy is uncertain, but in some cases, the condition can be cured, depending on the cause.


In advanced cases of Dropsy, your vet might be able to prescribe a course of broad-spectrum antibiotics for your fish that could be effective.


Sometimes, supplements to boost your pet’s immunity can be helpful. For example, you could try 0.3℅ of Potassium Dichromate to combat infectious agents, and herbal supplements can also be effective against Aeromonas hydrophila bacteria.

Improve water quality

Poor water quality stresses your fish, weakening their immune system. 

Be sure to change at least 30% of your tank water every week, clean your filter media every few weeks, and replace it when necessary to keep the environment healthy for your fish.

Is dropsy fatal in goldfish?

Dropsy can be fatal in goldfish, especially if you don’t treat the underlying problem promptly.

Be vigilant, and treat your fish for bacterial or parasite infections promptly to keep your fish safe.

Goldfish and Swelling

There are several causes of swelling in goldfish. However, most are caused by bacterial infection or parasite activity.

Keep your goldfish’s environment healthy by carrying out regular cleaning routines and filter maintenance. Don’t overfeed your fish; provide safe tank decorations that won’t injure your fish, and be sure to use an aquarium water testing kit to monitor the levels of nitrates and other harmful chemicals in your tank water.

Early treatment of minor infections can help to prevent more serious conditions, such as Dropsy, from developing. So, be vigilant and act as soon as you notice a problem.