17 Common Guppy Diseases, Parasites & Remedies

There are several parasites and diseases that plague guppies. However, there are also many remedies to help cure most of the diseases and get rid of the parasites. Here are the most common guppy diseases and infections as well as how to prevent and cure them.

How To Prevent Diseases That Affect Guppies

Guppy Diseases

  • Keep water parameters and temperature at the required levels.
  • Feed your fish well, but do not overfeed.
  • Maintain your tank regularly, perform weekly partial water changes.
  • Extract any dead fish immediately from your tank.
  • Examine your fish visually on a daily basis.
  • Take out sick fish from your main tank and place them into a hospital tank.
  • Before introducing new fish to your main display tank, keep them in a quarantine tank for 3-4 weeks.

Treating Sick Guppy

Depending on the illness you will need to treat only one fish or the whole tank. Before applying any medication to your tank, remove the activated carbon media from your filter, because this can neutralize the medication. Put it back once the treatment is successfully finished.

Always read the labels on the medication and follow instructions. Never use more treatment than instructed. After treating your fish, do a water change to remove the excess medicine from the water.

Most Common Guppy Diseases

Always keep medication at home in the event that you need to cure any of the following common sicknesses that can affect guppy fish.

White Spots

White spots that occur on the body of your guppy fish are also known as ick or ich. Ick is caused by an ectoparasite (ciliate protozoan Ichthyophthirius multifiliis) that is easily detected.

When a fish has ich it rubs its scales against rocks, plants, or decorations in the aquarium. Some fish suffering from white spots may also lose their appetite. Of course, small white spots also appear on their fins and scale.

Aquarium salt is one way to cure ick but there are also various medications that you can use to get rid of white spots on your guppy fish.

How To Cure White Spots

  1. Increase the water temperature slowly to 80 F.
  2. Add your medication with the recommended dose
  3. Alternatively, add aquarium salt at a rate of 1 teaspoon per gallon.
  4. Do this for 4-7 days.
  5. After, decrease the water temperature slowly back to normal.
  6. Do a partial water change of about 70%. Remove as much of the substrate as possible.

You can cure your fish of ick in a hospital tank; but you also have to apply the medication or salt to the tank, where the fish got sick.

Velvet (Oodinium)

Velvet disease causes your fish to develop tiny gold colored dots on its body. Velvet is contagious and can spread to all your fish in a short period of time.

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The early stages of the disease are difficult to spot and by the time owners realize that their fish are infected it is too late. Velvet causes fish scales to peel off and the fish start to bleed.

How to Cure Velvet

  • Velvet can be cured with copper medication such as Seachem Cupramin (if detected early).
  • Turn off the lights in or around the aquarium when applying the medication.
  • Do a 70-90% water change once your fish are symptom-free.

Fin, Tail Rot

A bacterial infection can cause guppy fins and tails to rot. A fungus that grows on nipped fins can also cause fin and tail rot. Another cause of fin and tail rot on fish can be ammonia burns due to poor water quality.

Depending on what causes the fin or tail rot, the treatment is different. Bacterial infections and fungus are treated in different ways.

If the fins and tail show no signs of damage but suddenly start rotting then its most likely a bacterial infection. On the other hand, a damaged fin or tail that starts rotting is most likely due to a fungus problem.

How to cure fin, tail rot

  • Move the sick fish to a hospital/quarantine tank.
  • Treat bacterial infections with an antibiotic such as Maracyn, Maracyn 2, Tetracycline, or Seachem ParaGuard.
  • Treat fungus problems with medication (see online fish stores or local pet shops) – always follow instructions.
  • For “ammonia burnsâ€, try to keep your fish in high-quality water.


Protozoa is a tiny parasite that is harmful to fish, especially guppies. The parasite clings to fish and penetrates the scales in order to enter the fish’s bloodstream. Protozoa infections usually occur in unheated tanks that are not frequently maintained.

How to treat protozoan

  • Use a heater to your aquarium and keep a stable water temperature.
  • In the early-stage, Malachite Green or Formalin can cure protozoan infections.
  • In more advanced stages, copper medicine such as Seachem Cupramine is better to use.
  • After treatment, do a 50-70% partial water change.

Columnaris & Mouth Disease

Its name is derived from columnar shaped bacteria, which are present in virtually all aquarium environments, though it has also been referred to as the cotton wool disease, saddleback disease, guppy disease, or cottonmouth disease.

The sick guppy will have trouble swimming as the bacteria paralyzes its muscles. They also lose interest in eating. The bacteria are contagious and can spread quickly to other fish.

How to treat Columnaris and mouth fungus

  • Starting treatment as early as possible is the key to successful curing of ColumnarisThe key to successfully cure Columnaris.
  • A Maracyn antibiotic or Formalin can cure cottonmouth disease.
  • Adding aquarium salt to your tank can also be effective.
  • Do a 50% water change and add one teaspoon of salt per gallon every day for 3 days.
  • Leave the salt in the water until the fish are cured. Perform a 50-70% water change after you are sure that they are cured.
  • A 30 minutes potassium permanganate (KMnO4) bath can also cure Columnaris.
  • Potassium permanganate is a powerful oxidizing agent and you should not exceed 10mg/l in the water, because it can burn the fish.


Bacterial infections that infect the liver or kidney of guppy fish is referred to as dropsy. Dropsy disease causes the abdomen of fish to swell with fluid that is not expelled.

The guppy fish swells up and discoloration occurs. The fish will have problems swimming and eventually die. Dropsy can be a result of water pollution, overfeeding, or a genetic disorder.

How to treat dropsy

Unfortunately, there is no cure for dropsy caused by a bacterial infection. By the time symptoms appear, the damage in the fish’s internal organs has already progressed beyond repair.

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Swollen Gills and Gasping

Guppies take in water through their mouths and pass it over their gills in order to extract oxygen. They use an organ called a rake to do this which is similar to the human lung (in function).

Excess ammonia in the water can lead to swollen gills. Dead fish, fish waste, and excess food in the water can cause a build of ammonia.

Ammonia in low quantities will burn the gills, which will become inflated. In higher quantities, ammonia is deadly. Swollen gills can cause guppies to come to the surface and gasp for air.

How to treat swollen gills

  • If you notice that your guppies are gasping for air or have swollen gills then do a water change right away.
  • Keep a close eye on the water parameters during the next few days and test for ammonia.
  • Do not feed the fish for a few days, because feeding can cause ammonia spikes.
  • Adding nitrifying bacteria like API Quick Start to the tank can help.

Red Blood Spot

Ammonia or nitrites poisoning can also cause red blood spots to appear on the stomach or body of guppy fish. It’s a common occurrence in uncycled aquariums.

If you introduce guppy in a new aquarium, the ammonia and nitrite level will rise quickly because there are not enough beneficial bacteria to transform these compounds into nitrates. Both ammonia and nitrite are toxic to fish and can lead to poisoning and damage to fish.

How to treat red spots

Red blood spots cannot be cured. However, it is possible to save the fish if the poisoning level is not too high and you take action in time. Always allow new tanks to cycle for at least 2 weeks before introducing fish. 6 weeks is preferred. Prevention is better than cure in this case.

Viral Hemorrhagic Septicaemia (VHS)

Viral hemorrhagic septicemia is caused by a virus that infects the blood of guppy and other fish. Lesions appear on the body followed by ulcers and sores. The fins also start to rot after a while.

Other symptoms of VHS include pale gills and bulging eyes. The guppies will stop eating and their color will darken.

How to treat viral hemorrhagic septicemia

  • Treat all your fish with an antibiotic like Maracyn 2 or API Furan 2 can help cure VHS
  • Change the water in the tank after treatment is complete.

Popeye Disease

Fish pop-eye can be caused by a wide range of factors, therefore it is very hard to treat. Popped eyes can occur due to bad water quality, bacterial infection, dropsy, fungus, tuberculosis or other internal parasites. Pop-eye might not be deadly, but it can cause blindness to your fish. Unfortunately, it is very hard to cure popeye because it is not easy to determine the root cause.

Swim Bladder Disorder

The internal organ which helps fish control their buoyancy is known as the swim bladder. It helps fish keep their balance while swimming.

Swim bladder disorder in guppies is usually caused by stress. For example, moving guppies from a shallow tank to a deep-water tank. The guppy float at irregular angles or upside down and lose control of their swimming and balance.

Swim Bladder Inflammation

Swim bladder inflammation is caused by a virus and unfortunately cannot be cured. Fish with such symptoms should be removed from the tank and euthanized. Usually characterized by apparent swimming on the head.

Gill Flukes, Gill Worms

These are tiny white worms that you can see with your naked eye on the gills of your guppy. They can cause your guppies to bleed and to have trouble breathing.

How to treat gill flukes

  • Treat the whole aquarium with special medication following the instructions on the package. Usually, the early stages of gill fluke are curable.
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Gill worms are introduced in your aquarium usually by adding new fish or plants. This is why it is necessary to keep newly purchased fish in quarantine.

Camallanus Internal Worm

Camallanus is a common parasite found in guppies. It can be 0.8 inches in length and sticks out of the guppies anus. It is usually brown or orange in color and wriggles like a worm. Other fish may attack the Camallanus sticking out of infected fish.

How to cure Camallanus parasite

  • Camallanus is usually treated with Levamisole also known as Ergamisol for at least 5 days.
  • Fenbendazole and Parcide X or D work as well.
  • Do substrate vacuum and complete filter cleanse after.
  • Do a water change: 70-90%
  • After 3 weeks repeat the Levamisole treatment, clean filter and vacuum the substrate again.

Hexamitiasis – Hole in the Head or Body

Hexamitiasis is caused by a protozoan parasite, Hexamitia. It is usually rare in guppies. However, guppies infected with Hexamitia produce white, stringy feces and their colors become pale.

The infected guppy loses their appetite and eventually refuses to eat. In other fish species, one ore multiple holes will appear on their head. In guppies, these lesions appear on their bodies.

Hexamitiasis usually occurs in overstocked aquariums, where filtration is not sufficient. The lack of oxygen and water changes can also lead to Hexamitiasis.

How to cure Hexamitiasis

  • Hexamitiasis is usually treated with metronidazole also known as Flagyl.
  • The best way to treat Hexamitiasis is through medicated food.
  • If the fish refuses to eat, the medication should be applied to the water at a dosage of 250 mg / 10 gallons once a day for at least 3 days.

In the US metronidazole is available at most pet shops, however, in other countries, it can only be purchased with a veterinary prescription.

Bent Spine (Scoliosis)

Genetics or environmental factors can lead to scoliosis in guppy fish. Commonly referred to as a bent spine or crooked spine it usually occurs in young fish.

A guppy with a bent back will have difficulty swimming. Genetically, scoliosis is caused by inbreeding. They will have slower growth rates, swimming problems, and are weaker than other fish in general. They also have shorter lifespans. Sadly, there is no cure for bent spine and it is not contagious; however, it can be inherited by the offspring.


Tuberculosis is caused by bacteria called mycobacterium. The first sign of this disease is a lack of appetite, followed by hollow belly, ulcers on the body around the anus, fin and tail rot, discoloration.

Guppies suffering from tuberculosis die slowly. The disease can also be passed from one fish to the other by birth or through cannibalism. All dead fish should be removed from the tank and sick fish should be quarantined.

You can try to treat the sick guppies with neomycin, kanamycin or isoniazid antibiotics. However, if there is no improvement it is best to euthanize the guppy.

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