7 Common Goldfish Diseases: Are Your Goldfish Sick?

Photo by Annie Roi (Flickr)

Thank you everyone for such amazing responses to my goldfish disease symptoms guide. As you know, it’s very important to catch common goldfish diseases early. The guide received over 100 responses, and I was so happy to help so many goldfish hobbyists create healthier environments for their fish.

I originally wrote a follow-up article about common goldfish diseases and how to prevent them, but the article was nearly 6,000 words of content. So I decided to make this article a three-part series instead.

• The first part in the series covered goldfish disease symptoms and gave you a list of fourteen behavioral and physical signs to look for when observing sick goldfish.
• This is the second part in the goldfish disease series, and here we’ll examine seven of the most common goldfish diseases that affect freshwater aquariums and ponds.
• The third part in the series covers goldfish disease prevention and ways you can find and combat problems that may result in infection.

If your goldfish are acting strangely, rubbing against objects in the aquarium or resting listlessly at the bottom of the tank, you know something is wrong. It’s especially alarming when your goldfish start developing cotton-like growths and discolored patches along the scales and fins.

Goldfish are hardy. It is unusual for them to get sick. – David E. Boruchowitz, author of Aquarium Care of Goldfish

Some goldfish are so good at withstanding common goldfish diseases that they can safely be kept in freshwater ponds. So what’s going on?

Goldfish may be hardy, but they’re not invincible.

Goldfish will fall victim to parasites, bacterial infections, and fungal diseases if kept in poor water conditions. If not treated and left to spread, these common goldfish diseases can take over your fish until their weakened bodies have exhausted themselves fighting.

The good news: If you catch common goldfish diseases early and treat them quickly, your goldfish will thank you by staying happy and healthy for years.

But be careful! Stay observant. Never medicate the aquarium without knowing for certain what the problem is.

Are Your Goldfish Actually Sick?

Certain types of goldfish have been bred to develop strange, yet very fascinating, traits. As your goldfish mature, they may develop special characteristics specific to their breed.

But don’t confuse these qualities with common goldfish diseases!

If you don’t know what you’re getting into, you might mistake the elaborate noses of pompom goldfish for fungal infections. If you treat the poor little ones unnecessarily, you’ll stress them out and they might become infected with real goldfish diseases as a result!

Medicating the aquarium with a treatment your goldfish don’t need is stressful. This stress will then lower the immune system and your goldfish might actually start developing common goldfish diseases when they really were quite healthy before.

Know your goldfish types. Most importantly, do your research!

Below are five goldfish with qualities that might be mistaken for common goldfish diseases.

• Pompom Goldfish – Pompom goldfish (also referred to as pompon goldfish) are known for their nasal outgrowths on the right and left side of their head. The puffy growths can become so elaborate that they resemble cheerleader pom-poms. But rest easy. These outgrowths are normal. Don’t mistake them for fungal infections!
• Lionhead Goldfish – Lionhead goldfish develop a pretty impressive head growth that looks somewhat like a lion’s mane (hence the name). The head growth not only develops on the top of the head (like an oranda), but it also grows on the cheeks and gill plates. As your goldfish age, their head growths will become much more defined (and can get quite large). Again, this unique characteristic shouldn’t be confused with common goldfish diseases.
• Oranda Goldfish – Like the lionhead, oranda goldfish have fleshy raspberry-shaped growths on the top of their head. This head growth is called the wen (or hood). While normal for oranda goldfish, the wen can grow so large that it sags down over the eyes and blocks the goldfish’s vision. Some hobbyists even confuse the wen for common goldfish diseases.
• Bubble Eye Goldfish – Bubble eye goldfish are named after the fluid-filled sacs that develop beneath their eyes, similar to large but fragile balloons. You might notice that these fluid-filled sacs keep growing. Sometimes the sacs can become so enlarged that it almost appears as though the eyes are looking directly up at the aquarium lights. The sacs under their eyes can easily break if there are sharp objects or rough substrate in the aquarium.
• Telescope Eye Goldfish – Telescope eye goldfish are known for their protruding eyes that almost resemble telescope lenses. But don’t confuse these swollen eyes with a bacterial infection, one of the many common goldfish diseases that affect freshwater aquariums. Unless one eye is abnormally larger than the other, your goldfish are probably just fine.

As you keep goldfish and observe how they interact with their environment, you’ll learn more about their characteristics and traits, what they like and dislike. You’ll become so accustomed to their normal behaviors that you’ll be able to tell right away when something goes wrong.

If you’re on this page, most likely you know your goldfish are sick. And they need help.

Let’s pinpoint the problem and treat those common goldfish diseases.

Effective Treatments for Common Goldfish Diseases

Photo by Mikhail Esteves (Flickr)

Your goldfish aren’t acting the way they should. What should you do?

First, remove the sick goldfish.

Unless the whole tank is infected, quarantine sick goldfish and place them in a hospital tank. This will make treating common goldfish diseases much easier. As mentioned earlier, you don’t want to treat healthy fish unnecessarily. Doing so can cause your goldfish stress (and stress should always be avoided whenever possible).

If the goldfish disease is contagious, like white spot disease and most parasite infections, you can safely treat the infected aquarium without quarantining your fish. Of course, especially sick goldfish can still be placed in a hospital tank for special treatment if they’re in pretty bad shape.

After your goldfish are quarantined, you’re ready to begin treatment. Let’s take a brief look at 7 of the most common goldfish diseases that impact aquariums and ponds.

Goldfish Disease #1: White Spot Disease (Ich)

Very common in aquariums, white spot disease usually affects new goldfish that are stressed out after a long car ride (or shipment) home.

• Causes of Ich – White spot disease is caused by ich parasites in the water. These parasites attack stressed out goldfish with lowered immune systems, especially recently purchased fish. Anything that causes stress can make your goldfish susceptible to common goldfish diseases, so keep your aquarium water healthy and avoid drastically changing water temperatures.
• Ich Symptoms – If your goldfish are covered with what appear to be small grains of salt, the aquarium is probably infested with ich. Goldfish with white spot disease will also breathe heavily and scratch themselves against tank objects, even the aquarium walls.
• Ich Treatment – I suggest treating your goldfish with the salt and heat method mentioned in my ich treatment guide before looking into commercial medications. If you don’t notice improvement after a week of the salt and heat method, use Mardel’s CopperSafe (make sure there aren’t any invertebrates in the aquarium). You can find detailed instructions on how to treat your fish in the ich treatment guide above.

Keep up treatment for a minimum of 3 to 5 days after the last signs of white spot disease. Sometimes white spots can reappear if you stop treatment prematurely.

Goldfish Disease #2: Floating Problems (Swim Bladder Disease)

Fancy goldfish are commonly observed with buoyancy problems, and sometimes these floating problems will be incorrectly termed as swim bladder disease. Often, floating issues aren’t caused by a swim bladder problem at all and instead a result of other common goldfish diseases.

• Causes of Floating Problems – Your goldfish might experience floating problems if they are overfed, fed poor quality food, or not fed enough fiber. Dry floating pellets can sometimes cause fancy goldfish problems when the pellets absorb liquids and expand in the digestive tract. Constipated goldfish or goldfish with excess internal gas may also experience difficulty swimming. Genetic floating problems can even occur after a spawning (in this case, there is no treatment).
• Floating Symptoms – If you notice your goldfish swimming erratically, swimming sideways, or even swimming upside down, your goldfish are having buoyancy problems. Goldfish may also look physically swollen or bloated.
• Treatment for Floating Problems – Test the water and make sure the water is clean, since unhealthy water is one of the main causes of common goldfish diseases. In part three in this series, you’ll find out how to solve problems with poor water quality. After water conditions are healthy again, fast your goldfish for 3 days. If your goldfish are still having trouble swimming, try feeding them veggies and low-protein foods. I recommend frozen peas (see my guide here. Some hobbyists also recommend daphnia to treat constipation.

Complete weekly water tests with a freshwater test kit (I use API’s Master Test Kit) and keep a watchful eye on ammonia, pH, nitrite, and nitrate levels. Continue feeding veggies and daphnia to your goldfish. Your goldfish should be swimming fine within a few weeks.

Goldfish Disease #3: Fin Rot (Tail Rot)

Goldfish under a lot of stress might develop fin rot, a bacterial infection also known as tail rot. Fin rot is usually a secondary infection that may infect your fish if they’re already stressed from another goldfish disease or injury.

• Causes of Fin Rot – Stress will make your goldfish susceptible to certain types of bacteria. Common goldfish diseases, poor water quality, overcrowding, sudden temperature changes, fin nipping, or aggressive fish can all cause the immune system to lower and fin rot to develop.
• Fin Rot Symptoms – Your goldfish will show signs of fin rot if they have ragged, torn, or red-streaked fins. If allowed to get worse, the edges of torn fins will become white as bacteria eat away the fins on your goldfish. The bacteria infection might become so bad that it will completely deteriorate fins to the body tissue. If the disease is allowed to spread to the fin base, your goldfish cannot regrow their fins. So treat fin rot early!
• Fin Rot Treatment – Good water quality is a must! So test that water. Your goldfish cannot start the healing process if water quality is poor. After the water environment is healthy again, treat the water with 1 teaspoon of aquarium salt per gallon of water. If you don’t notice an improvement after 5 days, move on to commercial treatments. Before treating, take out the active carbon from the filter. I recommend Maracyn-Two. It works great for many bacterial infections and uses minocycline as an active ingredient. Once you’re done with treatment, change out 25% of the water to get rid of excess salt. Continue your weekly water changes as usual.

Treat fin rot early. Don’t allow the bacteria to completely deteriorate the fins or your goldfish will not be able to grow them back. If treated quickly, you should notice signs of healing after a couple weeks.

Goldfish Disease #4: Fungal Infection

Your goldfish may develop fungal infections if water quality is poor. Fungal diseases can also affect goldfish that are already sick from other common goldfish diseases.

• Causes of Fungus – Stress and a lowered immune system will prompt fungus to grow. Goldfish suffering from parasitic infections, ulcers, or open wounds have a higher chance of also becoming infected with a secondary fungal disease.
• Fungal Disease Symptoms – Cotton-like growths along the body and fins are sure signs of a fungal infection. Fungal infections can be fatal if given enough time, as it will spread and attack other areas on the goldfish.
• Fungal Disease Treatment – As mentioned earlier, move infected goldfish to a hospital tank before treatment. Fungal diseases are not contagious. Take out the active carbon from the filter and treat the aquarium with Methylene Blue. Methylene Blue works great on sensitive fish and can be very effective when combined with aquarium salt to help your goldfish rebuild their slime coats.

Fungal infections should clear up after a couple of weeks, as long as you continue to keep the aquarium water healthy. Feel free to move your goldfish back to the main aquarium once all signs of fungus have disappeared.

Goldfish Disease #5: Gold Dust Disease (Velvet)

Very similar to white spot disease, gold dust disease or velvet resembles small grains of dust and starts on the backs of goldfish. These small parasites are smaller than ich and can be difficult to detect.

• Causes of Velvet – Like many common goldfish diseases and parasite infections, gold dust disease is usually found in tanks where new fish are present. Your goldfish might also be susceptible to velvet if water quality is poor or your goldfish are under stress.
• Velvet Symptoms – Goldfish with velvet might have a whitish-yellow film on their skin and what might appear to be golden specks of dust. Velvet will often start on the backs of goldfish before spreading to the body and gills. Velvet causes your goldfish to scratch against objects in an attempt to get the parasites off. If allowed to get worse, it might almost appear as if the slime coats on your goldfish have thickened or are even peeling off. Affected goldfish may also have clamped fins or show signs of heavy breathing or weight loss.
• Velvet Treatment – Since velvet parasites receive a portion of their energy from photosynthesis, cover the aquarium with a blanket and turn off the aquarium lights during treatment. Raise the water temperature to 80 °F (26 °C). This will quicken the parasite’s life cycle. Add 1/2 teaspoon of aquarium salt per gallon of water and remove the active carbon from the filter. Remove any invertebrates from the aquarium and treat the water with Mardel CopperSafe for 10 days. Once you’ve finished treatment, do a 25% water change and continue routine water changes as usual.

Continue treatment several days after the last signs of gold dust disease to ensure all parasites are exterminated. You should notice signs of improvement after a week of treatment.

Goldfish Disease #6: Anchor Worm (Lernaea)

Despite its name, anchor worm is not caused by a worm at all. One of the most common goldfish diseases in freshwater ponds, anchor worm is caused by Lernaea copepod crustaceans.

• Causes of Anchor Worm – Anchor worm can develop in tanks with recently purchased goldfish. If you don’t quarantine new fish or plants (purchased from tanks where fish were present), you may notice an outbreak of anchor worm after a week or two. You could also also be at risk of other common goldfish diseases if you don’t quarantine.
• Anchor Worm Symptoms – Look closely and you may notice whitish green hair-like creatures hanging from the bodies of your goldfish. The attached areas are also usually red and inflamed, often with raised ulcers around the wounds where female parasites embed themselves deep into the muscle tissue. Your goldfish may attempt to get the parasites off by rubbing against objects in the aquarium.
• Anchor Worm Treatment – Treat the aquarium with 1/2 teaspoon of aquarium salt per gallon. The salt will help prevent secondary infections and future parasite re-attachments. It will also guard against other common goldfish diseases. Now you’re ready for treatment.
  • Remove the active carbon from the filter. Then treat the aquarium with a commercial medication to kill off the parasites and stop eggs from hatching. I recommend Parasite Guard to cure anchor worm.
  • Some goldfish hobbyists also recommend using tweezers to remove Lernaea parasites from the fish. Be careful. Sometimes these parasites can burrow so deeply into the goldfish to cause harm. If using tweezers, I recommend using medication in the aquarium first to kill off the parasites before gently taking them out of the fish (gripping the parasite as close the wound as possible). Slip your goldfish underneath water every so often so they can catch their breath.

It might take a couple of weeks before signs of anchor worm disappear. Though, you may notice improvement (reduced redness and swelling) after a few days of using Parasite Guard. After treatment, change out 25% of the water to remove excess salt and continue routine water changes as normal.

Goldfish Disease #7: Fish Lice (Argulus)

Fish lice, also known as fish louse, are from the Argulus species of parasite crustaceans. They’re very common in goldfish ponds. They’re uncommon in freshwater aquariums though, unless new fish are brought in from an outside source.

• Causes of Fish Lice – Fish lice like to hop a ride on new goldfish that haven’t been treated in a quarantine tank. So make sure you always quarantine new goldfish to prevent common goldfish diseases.
• Fish Lice Symptoms – Fish lice have round greenish-brown, disk-shaped bodies. They’re often seen moving around the stomach, throat, and bases of fins. When lice attach to your fish, small red spots may be noticed around the wounds. Infected goldfish will try to rub against objects in the aquarium in an attempt to get the fish lice off.
• Fish Lice Treatment – Raise the water temperature slowly to 80 °F (26 °C) to speed up the fish lice life cycle. Add ½ rounded teaspoon of aquarium salt per gallon of water to help your goldfish guard against parasite re-attachments and other common goldfish diseases. Now you can treat the aquarium with medication.
  • I recommend Parasite Guard, as it works very well with external parasites. Parasite Guard includes Dflubenzuron as an active ingredient, which is very effective against fish lice.
  • In addition to medication, goldfish hobbyists recommend using tweezers to remove visible adult lice on goldfish. As with anchor worm, be careful when doing this and make sure you medicate the entire tank beforehand to exterminate free-swimming lice and prevent eggs from hatching.

A complete fish lice life cycle can take longer than that of many other parasites. So treatment for fish lice in an aquarium or outdoor pond may take up to a month. You should stop noticing signs of common goldfish diseases within a week though, often sooner.

Keep Your Goldfish Tank Disease Free

If you’ve followed the steps outlined in this article, your tank is on its way to staying completely free from common goldfish diseases. But it isn’t there yet!

You may have successfully battled nasty goldfish diseases this time around, but are you taking preventative measures to keep your goldfish safe? It’s important to determine what causes common goldfish diseases so you can take strives to prevent future tank nightmares.

We’ll talk more about this in part three of the goldfish disease series. Until then, maintain a healthy aquarium environment for your goldfish.

Photo by 22Lauren (Flickr)

Remember: One or two goldfish require at least 20 gallons (75 liters) at the very minimum to thrive (read more about this in my goldfish tank guide). In addition to a large aquarium, goldfish need routine water changes, weekly water testing, a nutritional diet, and a good filter to manage all that waste.

You should also be quarantining all new fish for a minimum of two weeks before introducing them to your healthy fish. After all, you don’t want your new pet to infect all of your goldfish if parasites decided to hop a ride before the drive home.

Goldfish care shouldn’t be taken lightly. Just like any pet, your goldfish need your ongoing love and attention. If you can give your goldfish the care they crave, they’ll reward you many times over with years of enjoyment. And it will go a long way to prevent common goldfish diseases.

How Do You Treat Common Goldfish Diseases?

What is your preferred method for battling common goldfish diseases? Have you successfully treated common goldfish diseases in your aquarium? What tips can you give other goldfish hobbyists? Write your responses in the comments below!