17 Common Guppy Parasites And Diseases (& How To Treat Them)

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Last Updated on 2023-12-18

Guppies are a popular pet fish. They are pretty to look at, with their fancy colors and tails. They are easy to care for and to breed. Guppies are hardy fish that can survive a wide range of conditions.

Guppies are so hardy that when something is wrong, it can be a surprise. Just like any other animal, fish, or living thing, they too can get sick. 

Guppies can get sick from infections, diseases, and parasites. There are diseases that they share with others, and there are ones that are unique to Guppies. 

Luckily, there are ways to prevent these diseases, infections, and parasites. There are ways to recognize them and treat them. Being a responsible guppy owner means learning the different illnesses, prevention, and how to treat them.

A Quick List of Guppy Fish Parasites and Diseases

Here is a quick list of the 17 most common Parasites and Diseases that affect Guppies that you should look out for. In the following sections, you’ll find detailed information on each one: how to recognize if your Guppy has it, what causes it, and how to treat it.

  • White Spots
  • Velvet (Oodinium)
  • Fin and Tail Rot
  • Protozoan (Guppy Disease)
  • Columnaris and Mouth Fungus
  • Dropsy
  • Swollen Gills and Gasping
  • Red Blood Spot
  • Viral Hemorrhagic Septicaemia (VHS)
  • Popped Eye Disease
  • Swim Bladder Disorder
  • Swim Bladder Inflamation
  • Gill Flukes, Gill Worms
  • Camallanus Internal Worm
  • Hexamitiasis-Hole in the Head or Body
  • Bent Spine (Scoliosis)
  • Tuberculosis 

Guppy Parasite and Disease Prevention

Before we get into the details of the diseases and how to treat them, it is important to note that the best treatment is always prevention. There are a number of things owners can do to help protect their guppies from diseases, parasites, and sickness.

  1. Be Informed Make sure you have all the information possible about guppy care. Certain breeds have special requirements, so also make sure that you have information on your specific Guppies and their needs.
  2. Water Temperature Make sure the water temperature in your tank is within safe levels. Guppies’ ideal tank water temperature is between 72 and 82 degrees Fahrenheit, 22 to 28 degrees Celsius.   
  3. Feeding Make sure your guppies are getting the proper amounts of food. Too little food or too much food can weaken their immune system and make them more susceptible to disease. Adults require food 1-2 times a day and no more than they can eat in 1-2 minutes. Guppy Fries need food 3-5 times a day and no more than they can eat in 1 minute.
  4. Tank Maintenance Make sure your tank and the water inside are clean. Do a full tank clean at least once a month. Make sure not to leave any chemicals on the tank. Weekly water changes will help prevent water contamination. 
  5. Dead Fish Immediately remove dead fish to prevent water contamination and the spread of sickness. If there is some question of how the Guppy died, make sure to keep an extra attentive eye on the remaining guppies.
  6. Daily Inspection Inspect your guppies daily, checking for any signs of illness or something that isn’t right. 
  7. Fish Removal If a fish exhibits any symptoms relating to a disease, sickness, or parasite, remove them from the tank immediately. Determine what they are suffering from and apply the proper treatment.
  8. Fish Quarantine When getting new fish, keep them separated or in quarantine for 3-4 weeks before introducing them to your guppy tank.

What Are Some Common Causes of Diseases or Parasites in Guppies?

Guppies are hardy fish. Healthy guppies can fight off most diseases with minimal treatment. There are a few things that can affect a guppy’s ability to fight illness. Stress, Overcrowding, Water Temperature, and Water Quality can all affect a Guppy’s immune system and make them more susceptible to diseases and parasites.


Stress can weaken a Guppy’s immune system making it harder for them to fight off illness. A number of factors can cause your fish to feel stressed.

In the wild, guppies have plenty of places to hide in order to protect themselves. If they are in a tank that does not provide enough hiding places, they can get stressed out. Make sure you have enough hiding places for all your guppies.

In addition, if you add any non-guppy fish to the tank, you can cause distress in your guppies. Guppies are peaceful fish, but not all other fishes are. More aggressive fish may scare or threaten your guppies.


Overcrowding can affect a Guppy’s immune system as well. Overcrowding can cause stress. It can also make it easier for illness or parasites to transfer from one Guppy to another. 

In general, you can keep about ten guppies in a 20-gallon tank. You need to make sure they have enough space for everyone and enough hiding places for them all. 

Temperature of Water

Water temperature that is too high can cause illnesses to spread quicker. It can also weaken the immune system of your fish and cause them stress. 

Water temperatures that are too low may cause stress and weaken the immune systems of your guppies. With weakened immune systems, they may get sick much easier.

Make sure to maintain a tank temperature of 72 to 82-degrees Fahrenheit, which is 22 to 28 degrees Celsius.

Water Quality

Water quality can affect your guppies through the introduction of illness and through the stress it causes their immune systems. Dirty water in the tank can turn your fish tank into a breeding ground for bacteria and parasites. 

Change out 30-50% of the water each week. Make sure the water you add is chlorine-free, has the right temperature, and has the right pH balance.

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Treating Sick Guppies

Check your guppies every day. Make sure to look for anything unusual or out of the ordinary. If anything looks wrong, remove them from the tank immediately. Even if it turns out to be nothing, you’ll be glad you didn’t risk your other guppies by leaving a potentially sick guppy in the tank. 

Once you remove the Guppy, take a close look at it to identify what might be wrong. If you are unsure of what is wrong, take your Guppy to the vet. Once you know what your Guppy is sick with, you can administer proper care.

It is always a good idea to keep the medications on hand so you can treat your fish immediately if you are sure of your diagnosis. Don’t risk it if you are unsure since the wrong medication can make your fish sicker.

Most Common Guppy Parasites & Diseases

Below are the most common Guppy Parasites and diseases. You can use this list to determine the most likely cause of your Guppy’s illness and the best ways to treat what they have.

White Spots

White Spots is one of the most common Guppy health problems. It is also sometimes called Ick and Ich. White Spots is deadly if not treated. An ectoparasite is the cause of White Spots.

Fish with Ich will start rubbing themselves against the rocks and things in their tank. They may lose their appetite. The most obvious sign of Ich is the appearance of white spots.

Treating White Spots

Treating White Spots is fairly easy. While taking your sick Guppy out of the tank and quarantining it will help. You need to apply the following treatment to your main guppy tank as well. You want to make sure there is nothing of the parasite left.

  1. Slowly raise the temperature of the tank water. You want to raise it at about 1 degree a day until you reach 80 degrees.
  2. Add 1 teaspoon of Aquarium salt for each gallon of water. Or you can use any number of White Spot treatment medications available at your local Petco or Petsmart.
  3. Keep the tank at these levels for at least four days and as many as seven days.
  4. Begin reducing the temperature 1 degree at a time until it is about 76 degrees.
  5. Change out 70% of the water to return it to normal salinity.

Velvet (Oodinium)

Velvet is uncommon in hobby tanks, but it is deadly if left untreated and spreads quickly. Velvet is unfortunately hard to recognize early on as the golden spots are quite small. If your fishes’ skins start peeling off or they start bleeding, immediately quarantine the sick fish and begin treatment for the rest of your fish.

Treating Velvet

If caught early, you can successfully treat Velvet. When you check your fish every day, look for golden spots appearing on their body or fins.

  1. Apply copper medication as instructed on the container. You can get some at any local Petco or PetSmart.
  2. Raising the water temperature slowly to 80-degrees Fahrenheit and dimming the light in and around your aquarium will also help.
  3. Wait until your fish are showing no signs of sickness.
  4. You can change 70% of the water out to bring the tank back into balance.
  5. Lower the temperature slowly back to normal.

It is important to note that Shrimp and Snails can get sick from the copper. Once it has been used in a tank, it is hard to get it out. You should not try to keep snails or shrimp in the tank after treatment.

Fin or Tail Rot

Fin or Tail Rot can be caused by a fungus or a bacterial infection. The fungus or infection takes hold where fish have been nipped in fighting. Dirty water and ammonia from rotting food can also cause Rot.

The fins of a guppy suffering from Rot may look stuck together. If the fins look damaged, then the Rot is most likely caused by the fungus. If there is no noticeable damage, then it is most likely that the cause is bacterial. It is important to know the cause since they are treated differently. 

Treating Fin or Tail Rot

To Treat Fungal Fin Rot: 
  1. Quarantine your fish in a separate tank.
  2. Treat Fungal infection with special medications. You will need to contact your vet for these. Follow instructions exactly.
  3. Clean out the tank to protect your other guppies.
  4. Return your guppy to the tank once treatment is successful and no symptoms are apparent.
To Treat Bacteria Fin Rot:
  1. Quarantine your fish in a separate tank.
  2. Treat Fungal infection with Maracyn, Maracyn 2, or Tetracycline.
  3. Clean out the tank to protect your other guppies.
  4. Return your guppy to the tank once treatment is successful and no symptoms are apparent.


Protozoan is also called Guppy Disease because it mainly affects guppies. It can affect other fish but not as severely. It is caused by parasites.

The parasite will attach itself to the fish and burrow in until it gets to the bloodstream. The parasites will usually develop in a tank with bad water quality and water that is not warm enough.

Treating Protozoan

  1. The first thing you need to do is add to keep the temperature at a stable and safe level in your aquarium. You can do this by purchasing an aquarium heater.
  2. If you catch Protozoan at an early stage, treat it with Formalin or Malachite Green.
  3. If Protozoan is in a more advanced stage, treat it with copper medicine.
  4. Once your fish treatment is finished change out 50-70% of the water. If the water quality was bad before, then changing out the water at the beginning should also be done.
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Columnaris and Mouth Fungus

This infection may look like a fungus, but don’t let it fool you. It is actually caused by bacteria. The bacteria form a colony that looks like a big white splotch on the mouth or middle. 

A fish suffering from Columnaris and Mouth Fungus will become paralyzed and slowly stop swimming. They may also lose their appetite. 

This bacteria is highly contagious. Mostly, it affects female guppies, but male guppies can also catch it. Without proper treatment, it can wipe out your whole fish colony.

Treating Columnaris and Mouth Fungus

To successfully treat Columnaris and Mouth Fungus, start treatment the minute you notice signs. You can quarantine your sick fish, but it might be best to treat the whole aquarium due to the possibility that other guppies are sick but not yet exhibiting symptoms.

  • Formalin or Maracyn can be used to treat this sickness. 
  • You can also add aquarium salt to help cure the disease. You want to change out 50% of the water then add one teaspoon of salt for each gallon of water in the tank. Do this for three days.
  • You can use a 30-minute potassium permanganate treatment as well. This treatment must be done carefully as it can burn your fish if it is too strong. Only use 10mg per Liter. 
  • Once Guppy treatment is successful change out 70% of the water.


Dropsy is a bacterial infection that affects the liver and or kidneys. It can cause fluid to fill the abdomen. Your fish will appear swollen, distorted, and discolored. Scales may appear like spines on a pinecone, sticking out instead of lying flat.

The bloating will make it hard for your fish to swim. A number of things may cause Dropsy, including:

  • Water pollution
  • A bad diet
  • High stress
  • Genetic disorders

Treating Dropsy

Unfortunately, Dropsy is untreatable. Once the symptoms present themselves, the fish is already too sick to cure. All you can do is try to make your Guppy’s last days the best they can be. 

Separate any guppies that have Dropsy, and you can treat them to an Epsom salt bath. This bath will help make them more comfortable but will not cure their sickness. Use two tablespoons of salt for one gallon of water. Put the fish in for 30-45 minutes. Make sure the water is at the same temperature as your tank.

Swollen Gills and Gasping

Gills are a fish’s way of breathing. Swollen gills will cause a fish to gasp for air at the surface of the water. 

Swollen gills can be caused by too much ammonia in the water or carbonate poisoning. Ammonia usually comes from decomposing fish food, organic waste, and fish waste. Carbonate can come from the rocks and substrate in the tank.

Treating Swollen Gills and Gasping

  • If you notice your guppies are gasping and trying to get air or if their gills are moving more rapidly than is normal, you need to change at least 50% of the water.
  • Monitor your water and test for ammonia for 3-5 days.
  • Take a break from feeding your guppies for a couple of days. For adults, they can go up to ten days without food. Guppy Fry can only last three days.
  • API Nitrifying Bacteria can also help. 

Red Blood Spot

Red Blood Spot will usually appear on a Guppy’s body. Red Blood Spot is usually caused by ammonia or nitrites poisoning

If you recently got a new tank, then the tank may be the problem. A new tank can take up to six weeks to fully cycle and be safe for fish.

Treating Red Blood Spot

Unfortunately, there is no treatment. However, if you catch it before your fish has been severely poisoned, you can save your fish. Prevention is the best course of action.

  • Make sure to cycle your tank for three to six weeks.
  • Once you put your fish in, keep testing the water using an aquarium testing kit. You are looking for 0 parts per million Ammonia, 0 ppm Nitrite, and 10-40 ppm Nitrate.
  • Change the water frequently to help keep the levels safe. Once a week may not be enough. Change out at least 50% each time.
  • Skip a feeding or two for your fish. This will help prevent the addition of more ammonia.
  • You can also add live plants to your aquarium. They can be beneficial since some of them absorb ammonia.

Viral Hemorrhagic Septicemia (VHS)

Viral Hemorrhagic Septicemia is also referred to as VHS. A virus in the bloodstream is the cause of VHS. The first signs are lesions on the body of your fish. As the illness progresses, sores and ulcers will begin to appear. 

Other symptoms include fins rotting, bulging eyes, and turning pale. Eventually, your fish will begin to refuse food and become darker in color.

Treating Viral Hemorrhagic Septicemia

  • There is only one treatment for VHS. You need to treat your whole tank and all your fish with an antibiotic. Maracyn or Maracyn 2 are good options.
  • When treatment is complete do a 70% water change.

Popped Eye Disease

Pop-Eye or Popped Eye Disease is very hard to treat as it can be caused by a number of things. Knowing how to treat it means knowing the cause, and it is often hard to determine the exact cause for it.

Causes include:

  • Lack of clean water
  • Dropsy
  • Bacterial Infection
  • Fungus
  • Tuberculosis
  • Internal parasites

Treating Pop-Eye Disease

  • Quarantine your sick fish.
  • Take your fish to the vet. 
  • If the vet can identify what is wrong, then follow their directions.
  • If the vet is unable to identify what is wrong, you can try the treatments mentioned here. However, if you use the wrong treatment, it could make things worse.

Swim Bladder Disorder

Swim Bladder Disorder is rare in Guppies, but it can affect them. It is most commonly caused by stress. You may notice them bobbing at a weird angle or even upside down. It will appear as if they have no control, and they don’t. Bad water and High ammonia can also cause Swim Bladder Disorder. 

Treating Swim Bladder Disorder

  • Change out 70% of the water and test it to make sure there is nothing harmful in it.
  • Raising the temperature of the tank to 78 or 80 degrees can also help.
  • Check and see if anything is causing your guppy to stress out. If there is do whatever you can to relieve that stress.

Swim Bladder Inflammation

Swim Bladder Inflammation is easy to identify. The first signs will be similar to those of Swim Bladder Disorder. Your fish will begin swimming in strange ways. 

Next, you will notice the belly distending and swelling. A virus is the cause of Inflammation in the Swim Bladder. 

Treating Swim Bladder Inflammation

Unfortunately, there is no treatment for Swim Bladder Inflammation. It is highly contagious, so you need to remove your sick Guppy immediately. There is nothing you can do for your fish. It is best to give them a quick death so they do not have to suffer anymore.

Gill Flukes, Gill Worms

Gill Flukes, also called Gill Worms, can be seen with the naked eye. They are small worms that will invade your Guppy’s gills and live there. 

They cause your Guppy’s gills to bleed. In addition, you will notice your Guppy is having trouble breathing. They may be lying at the bottom of the tank or at the top, gasping for air.

Gill Flukes are usually introduced to aquariums by outside fish and plants being added. This is one reason why you should quarantine your new fish and plants is important. They can also spread more rapidly if the water is not clean enough.

Treating Gill Flukes, Gill Worms

There is only one treatment that works: a special medication you can get from your vet. Follow the directions carefully and treat your whole Guppy Tank. 

Guppies with Gill Flukes can be saved. However, if they are at the stage where they have started bleeding, then there is little you can do. Even with the Gill Worms gone, the bleeding will lead to death.

Camallanus Internal Worm

Camallanus Internal Worm is one of the most common health problems for guppies. It is a parasite that can reach up to 3/4 of an inch. Part of the parasite is visible sticking out of the anus of your fish.

You can tell it apart from fish waste because it moves like a worm, doesn’t leave the fish, and is orange or brown in color.

No one is completely sure where the parasite comes from. However, breeders have noted that it is more prevalent in guppies that are kept outside or fed Cyclops.

Treating Camallanus Internal Worm

The good news is that this parasite is treatable.

  1. Treat your fish with Levamisole for a minimum of five days. Other treatments are available, talk to your vet or fish expert.
  2. After treatment, perform a complete cleaning of the aquarium including a substrate vacuuming and filter cleaning.
  3. Do huge water changes of 70-90%.
  4. Three weeks later repeat steps one and two again. Followed by one more huge cleaning.

Hexamitiasis-Hole in the Head or Body

Hexamitiasis appears as a hole in the head or body of your fish. Hexamitia is a protozoan parasite that causes Hexamitiasis. This parasite is rare, but it does occasionally strike Guppies. 

The first sign of Hexamitiasis is fish waste that appears white and stringy. Then their colors began to pale. They will refuse to eat. Lesions will eventually appear. Most often, they are on the body of the Guppy.

Treating Hexamitiasis

  • Metronidazole (also called Flagyl) is typically used to treat Hexamitiasis. 
  • Medicated food is the best and easiest way to get the medication into your fish if you catch the illness before they stop eating.
  • If your guppy has started refusing to eat, you need to apply the treatment to the tank water. Use 250 mg for every 10 gallons of water. Do this once a day for three days.

Bent Spine (Scoliosis)

Bent Spine or Crooked Back isn’t common, but it isn’t rare in guppies either. It can be caused by environmental factors or genetics. This disease is usually noticed while guppies are still fries. 

Sometimes you will notice it when looking from above. Other times you may need to be looking at the fish from the side. It is best to check your fish from all angles in order to catch this. 

Guppies with Scoliosis will have trouble swimming

If your Guppy is swimming upside down, however, It can be a sign of something else. Find out what it means here! They are often weaker and may have a shorter life span. In addition, they may be bullied by others, making them stressed and more susceptible to illness.

Treating Scoliosis

There is no treatment for Bent Spine. Luckily, Scoliosis can not be passed from fish to fish like bacteria, parasites, or viruses.  However, a mother or father guppy with Scoliosis can pass it on to their offspring. There is a high probability of most of the offspring being born with this genetic deformity. 

This is not a deadly disease, and a guppy can still have a good life. Make sure to feed them well and give them plenty of places to hide.


Mycobacterium is the bacteria that causes Tuberculosis. In fish, it presents at first a lack of any desire to eat. The following symptoms show the progression of the disease.

  • Hollow-belly
  • Ulcers on the body near the anus
  • Fin and tail rot
  • Discoloration

Tuberculosis in fish will cause death if not treated. In addition, it can be passed on to other fish in the tank. 

Treating Tuberculosis

Tuberculosis is not easy to treat in fish. 

  • If any of your fish are dead, remove them from the tank so that they will not infect your remaining fish.
  • If you catch it before your fish dies, quarantine them in another tank. 
  • Treat your sick fish with Neomycin, Isoniazid, or Kanamycin antibiotics.
  • If your fish does not improve, you should quickly euthanize them to end their pain and protect others from getting sick.

While rare, Tuberculosis can be passed to humans. It is important to be careful while treating your fish. Make sure you are wearing a mask and gloves. Also, make sure you have no open cuts or wounds in which the bacteria could get into you.



Here are some frequently asked questions about Guppies and sickness.

Do Guppies Have Parasites?

Yes, Guppies can get parasites. 

  • White Spots is caused by an Ectoparasite.
  • Velvet is caused by a parasite called Oodinium.
  • Guppy Disease (Protozoan) is caused by the Protozoan Parasite.
  • Pop-Eye Disease can be caused by a parasite.
  • Gill Flukes is caused by Gill Worms which is a parasite.
  • Camallanus Internal Worm is a parasite.
  • Hexamitaisis is caused by a Protozoan Parasite.

Can Guppies Survive Ich?

Yes, Guppies can survive Ich or White Spots with the proper treatment. Curing Ich is not that hard, especially in comparison to some of the other health issues guppies can have.

What Are the Signs of Parasites in Guppies?

Signs of parasites will be different depending on the parasites.

  • White Spots is caused by an Ectoparasite.
  • Velvet is caused by a parasite called Oodinium.
  • Guppy Disease (Protozoan) is caused by the Protozoan Parasite.
  • Pop-Eye Disease can be caused by a parasite.
  • Gill Flukes is caused by Gill Worms which is a parasite.
  • Camallanus Internal Worm is a parasite.
  • Hexamitaisis is caused by a Protozoan Parasite.


Guppy illness is most often caused by overcrowding, bad conditions, and the introduction of sick fish to the tank. The best way to keep your fish healthy is to take preventive measures to ensure your fish are as healthy as possible.

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