Top 5 Most Common Goldfish Diseases & How to Fix Them

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If you have a goldfish, you are likely to run into one of these most common goldfish diseases. Learn how they occur, how to fix your fish and how to prevent them from coming back! Goldfish diseases pictures are included below.

Remember: All disease processes are made WORSE by poor water quality. If you have a sick fish, check your water chemistry FIRST!

Buoyancy Disorders

The most common reason our service sees goldfish is buoyancy disorders. Positive or negative, a goldfish’s unique anatomy predisposes them to many issues. Goldfish are physostomous fishes, with a duct between their esophagus and swim bladder. They will swallow air to inflate and rise in the water column, while a separate gland removes the air and deflates the swim bladder. Vigorous surface feeding causing positive buoyancy is very common in hungry goldfish. This is often transient and can be fixed by switching to a sinking diet. It’s also why those “magical” green peas correct “constipation.” <– not an actual thing in freshwater fish

Fancy goldfish, with their unique anatomical features, are more prone to buoyancy disorders. Positive or negative, breeding fish for external features has caused considerable problems with their spines and swim bladders. Radiographs are required for diagnosis of fancy goldfish swim bladder disorders. Treatment for these fish is often prolonged and may not revert back to “normal” behavior.

goldfish diseases picture
Ranchu x lionhead fancy goldfish with positive buoyancy disorder

Learn more about Goldfish Buoyancy Disorders in our Fish Health Seminar series.

“White, Stringy Poop”

998 cases out of 1,000, the poop coming out of your fish is NOT a parasite. Trust me, I’ve seen that many cases. The only two that actually had confirmed GI parasites were with wild caught fishes. Goldfish are NOT wild caught and almost never come in contact with wild fish species. Treating for internal parasites in goldfish is a waste of time and resources, not to mention $$$.

White, stringy poop is usually an empty bowel movement, not an actual goldfish disease. It is a sign your fish’s GI is functional, there’s just nothing to come out along with it. We see this commonly in goldfish in very warm water (high 70’s to 80’s) and limited feedings. Goldfish metabolism churns along at the same rate regardless of when or how much they eat, so some bowel movements may have food, others not. Super water water will crank along metabolism faster, leading to more bowel movements and HUNGRY goldfish. Your goldfish tank should be around room temperature, 74-77F; they do NOT need a heater. If they are in a tank with tropical fish, expect their metabolism to be ramped up and lots of poop to shoot out their back ends.

Although this syndrome doesn’t need “treatment,” like other goldfish diseases, you may see fewer white, stringy poops by decreasing your tank temperature and feeding your goldfish smaller meals throughout they day.

Polycystic Kidney Disease

If your goldfish looks like a water balloon, there’s a chance he has polycystic kidney disease. We do not know what causes this in goldfish, but we see it quite a bit. It is not a contagious disease. Essentially, cysts form in the kidneys, causing kidney malfunction and the fish’s body to take on lots of water. Diagnosis is made via ultrasound. Other than palliative care, this disease is terminal. As long as your fish is swimming around, eating, and interacting with their tank or pondmates, they are not suffering. A fish that will not eat, cannot swim or maintain normal body position needs a veterinarian to perform humane euthanasia.

goldfish diseases polycystic kidneys
Euthanized goldfish with polycystic kidney disease

Neurofibromas aka “Warts”

Lumps on goldfish are a VERY common goldfish disease. Other than causing some aesthetic issues, they are not a threat in any way to your fish’s overall health. They are caused by benign neural neoplasia deep within your fish’s skin. We have tried everything to remove them and they always come back. Thankfully, most fish do not even know they are on their bodies. Most will grow a stalk, fall off and then regrow. Since treatment is unsuccessful, we’d rather not subjugate a fish to harsh treatment. If your fish is having problems eating or swimming due to a lump or wart, discuss your case with an aquatic veterinarian.

Comet goldfish with neurofibroma on dorsal ridge

Parasites aka “Itchy Fishies”

Parasites most commonly get into fish systems when new fish are added without proper quarantine. Fish in a store are already stressed out, and may have only been there a few days, so they may be sick without showing any signs. Then with added stress of capture, transport and a foreign environment, anything lingering on your new fish can take advantage and quickly overwhelm a compromised immune system.

Clinical signs of parasites include bruising, missing scales, torn fins, lethargy, increased respiratory effort, sudden death and flashing. Some macroscopic parasites, such as lice and anchor worms, can be seen without a microscope. In order for treatment to be successful, a correct diagnosis needs to be determined by your aquatic veterinarian. There is no one treatment that will cure all parasites.

Bruising on goldfish tail
Bruising on the side of a goldfish may be the only sign of parasites in your system.

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