goldfish and flukes all you need to know

Goldfish and Flukes : All You Need to Know

​Your Complete Guide To Understanding More About This Disease


These creepy little worms are commonly disgusting in fish just as head lice is to humans! 

Are you ready to learn more about these parasitic pests?

We will go over what the symptoms are and what to look for, so you know how to treat your goldfish for flukes!

By the way, flukes are very common in goldfish, but they can be fatal if left untreated.

fluke in goldfish

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What are flukes?

Dactylogyrus or Flukes are parasites that plague the aquaculture industry.

These blood-thirsty pests are repulsive. 

They are contracted from fish to fish and not a concern for humans.

The fish trade of freshwater fish (to include goldfish) typically originates in Asia.

The more trade that occurs worldwide of freshwater fish, the more widespread diseases become. 

There are two types of flukes:

  1. Gill flukes (Dactylogyrus)

  2. Skin flukes (Gyrodactylus)

Gill Flukes Life Cycle

  • Enough eggs are laid in the tank water to produce a massive amount of larvae.

  • After hatching, the larvae swim to a host fish and attaches itself in or around the gills.

Skin Flukes Life Cycle

  • Live young are released from the mother fluke.

  • These young flukes swim to a host fish and attach itself to the body of the fish.

goldfish flukes

Characteristics of Flukes

  • Worm-like body
  • Anterior suction cups 
  • Posterior hooks
  • Once attached to host, flukes inject bacteria through the insertion of their hooks.

What causes flukes in goldfish?

Just like any other disease in goldfish, poor water quality is the NUMBER ONE cause for stress in goldfish.

Stress leads to disease.

Flukes love dirty tank water!

When you couple that with an overcrowded tank (too many fish,) you have the perfect makings for a fluke fiesta. 

Flukes are present in almost every fish tank.

They are harmless if the water environment is ideal and there are no other contributing factors such as stress, overcrowding, or new diseased fish.

They hitchhike their way into an otherwise healthy tank.

New fish introduced to your tank often carry flukes.

This is why it’s imperative to quarantine your new fish and avoid contaminating your tank with the tank water in the transport bag your new fish traveled in.

Symptoms of Flukes

txgolden_waterpiggies pic 2


If you notice any of the following symptoms in your goldfish, treatment is necessary!

There is only one way to definitively diagnose flukes in goldfish, and that is through a gill biopsy or scale scraping.

These samples are placed on a slide and viewed under a microscope. Flukes cannot be seen with the naked eye.

Because we don’t all happen to have a microscope in our closet, we have to rely on other ways to determine if our goldfish have flukes.

  • Breathing issues such as gasping for air near the surface of the water.
  • Rubbing on surfaces such as tank walls, tank decor, etc.
  • Clamped fins (holding fins close to the body.)
  • Staying at the bottom of the tank.
  • Ulcers/sores 
  • Excessively covered in slime coat

Treatment for Flukes

The first thing to do is DON’T PANIC

Don’t rush out to your local pet supply store and start randomly buying treatments off the shelf all willy nilly!

Quarantining the infected fish is a hit and miss situation because parasites infect the entire tank.

As such, the whole tank should be treated as opposed to only treating the infected fish.

Never purchase a treatment containing formalin! 

Many parasitic treatments contain this toxic chemical and fish owners unknowingly put this in their tank, which does more harm than good.

Formalin is 37% formaldehyde mixed with water.

  • Highly toxic to both humans and fish.
  • Kills good algae in a tank.
  • Depletes the oxygen present in tank water.
  • Is a cancer-causing agent; carcinogen

kingkoigoldfish pic 5


Not sure what to use? Here are some recommendations.

We have taken the guesswork out of choosing a product to treat flukes in your goldfish.

Here are a few recommended treatments to use. We based our recommendations from reviews of fish owners as well as overall online ratings.

Each of the recommended products below does not contain harmful toxins and are safe to use with your goldfish.

Fish Zole – Metronidazole – 250mg

Antibacterial and Antiprotozoal Fish Medication

Metronidazole Antibacterial Fish Medication


Fish Zole is produced by Thomas Labs, which is a reputable company that is committed to developing products that heal your fish without any harmful effects. 

Both professional fish breeders and at-home hobbyists stand by this product because of its effectiveness. 

  • Effectively kills parasites (including flukes) and bacterial infections in goldfish
  • Safe to use
  • Treats bacteria released by flukes
  • Ingredient is Metronidazole, no harmful chemicals or toxins
  • Simply drop tablet into tank water
  • Can be used for treatment up to 10 days
  • Saltwater and freshwater fish


  • Follow directions on container.


Question: What is Metronidazole?

Answer: Metronidazole is an antibiotic that is used to treat bacterial and parasitic diseases in fish.

Question: What other diseases does this product treat?

Answer: Ich, anchor worm, flukes, fin rot, lice, and bacterial infections. 


Seachem ParaGuard 250ml


Seachem is a reputable product backed by research that is based on the well-being of your fish. 

This product is free from toxins that are commonly found in treatments used for parasites in goldfish. 

  • Not only kills parasites, but also kills fungal/bacterial/viral
  • Does not alter pH levels
  • Treats parasitic infections, fin rot, ich, and other diseases
  • Safe to use; not harmful to fish or humans
  • Saltwater and freshwater fish


  • DO NOT use in a tank containing invertebrates, corals, crustaceans, sharks, or rays.
  • Remove chemical filtration if you have any in the tank.
  • Dosing amount is 5 mL (1 capful) per 40L (10 gallons) of water.
  • Administer daily as directed as long as your goldfish do not exhibit stress. Monitoring for stress during treatment is essential.


Question: Is this safe to use in a tank even if all of the fish are not infected?

Answer: Yes. In all likelihood, if one fish is infected, the others will be too. Parasitic infections are highly contagious.

Question: What are the main ingredients?

Answer: Aldehydes, malachite green, and protective fish polymers.


MinnFinnTM Mini - Broad-Spectrum Treatment for Koi and Goldfish Diseases


Many fish owners reach for MinnFinn because of its broad-spectrum treatment ability.

Free from toxins while effectively killing flukes make this product a leader! 

  • One of the best broad-spectrum treatments for goldfish diseases
  • DOES NOT contain any toxins
  • Eradicates bacterial/fungal/parasitic infections
  • Treats flukes, anchor worm, ich, fin rot, mouth rot, and more
  • Easy to use
  • 2-3 treatments required for flukes


  • Follow directions on container.


Question: Can this be used for saltwater fish?

Answer: No. This is designed for Koi and goldfish.

Question: What are the main ingredients?

Answer: Active ingredients: hydrogen peroxide and peracetic acid. Also contains a prophylactic as a preventative.

txgolden_waterpiggies pic 1



Flukes are something you don’t want to ignore because your whole tank becomes infected and if left untreated, your goldfish will die.

Flukes are creatures that have no mercy on their victims and will eventually suck the life right out of them.

Assess the symptoms first and THEN treat with a product that is free from formalin or methanol. 

Now you have everything you need to know about how to treat your goldfish for flukes!

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