Guppy Diseases, Parasites & Remedies

Unfortunately, there are many diseases and parasites that can harm your guppy fish. The good news is that many of them can be cured. In this article, I will try to present to you the most common guppy diseases and infections, prevention, and remedies.

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Important: it is easier to prevent diseases than to treat sick fish!

The most common guppy fish diseases such as ick (white spot), velvet (gold dust), fin rot and flukes can be cured with the Seachem ParaGuard from Amazon.com medication.

Here are some very basic steps to prevent most diseases:

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

For more information about guppies, please read my guppy fish care guide, where I share my experience of more than 15 years of keeping guppies.

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Stress as a Precursor

Stress is a primary culprit behind most diseases afflicting guppy fish. When stressed, their immune systems weaken, making them more susceptible to infections and parasites.

Several factors can induce stress. In their natural environment, guppies are nestled amidst plants, tree roots, branches, and other natural hideaways.

To alleviate stress, ensure your tank mimics this natural environment. Live aquarium plants, in particular, make excellent hiding spots.

Overcrowding is another significant stressor.

While guppies are peaceful by nature, housing them with more aggressive species like bettas, gouramis, angelfish, or barb fish can lead to distress.

Temperature fluctuations, whether too low or excessively high, further stress guppies. It’s advisable to use a heater to maintain a stable water temperature.

Lastly, water quality plays a pivotal role not only in stress but also in disease onset. Regularly perform partial water changes (30-50%) each week. Ensure the new water matches the desired pH level, and temperature, and is devoid of chlorine.

Most Common Guppy Illnesses and Diseases

Guppy illnesses can range from external infections like Ich and Velvet to internal ailments such as Dropsy. Recognizing and understanding these common diseases is vital for ensuring the health and longevity of these popular aquarium fish.

Here is a list of the 17 most common guppy diseases:

• External Diseases
  • White Spots – Ich, Ick
  • Velvet (Oodinium)
  • Fin, Tail Rot
  • Columnaris & Mouth Fungus
  • Gill Flukes, Gill Worms
• Internal Diseases
  • Guppy Disease (Protozoan)
  • Dropsy
  • Red Blood Spot on Guppy Stomach/Body
  • Camallanus Internal Worm
  • Hexamitiasis – Hole in the Head or Body
• Physical and Behavioral Anomalies
  • Swollen Gills and Gasping
  • Popped Eyes
  • Swim Bladder Disorder
  • Swim Bladder Inflammation
  • Bent Spine (Scoliosis)
  • Fish Tuberculosis
  • Viral Haemorrhagic Septicaemia (VHS)

Important: in order to raise the chance of curing your guppies you should always keep medication at home for the following most common guppy diseases. 

Now let’s get into details about the common diseases that affect guppies.

White Spots – Ich, Ick

Probably the most common problem in the fishkeeping hobby is the white spots, also known as ich or ick. Ick is not deadly if treated in time.

Ick is actually caused by an ectoparasite (ciliate protozoan Ichthyophthirius multifiliis) and it is very easy to detect. The fish start rubbing their skin against rocks, plant leaves, decoration or to the sides of the aquarium. They can also lose appetite. You will notice small white spots on their skin and fins.

Curing ick is not that hard. There are various medications, but you can also use aquarium salt.

How to cure ick:

1. Raise the water temperature slowly to 80 F
2. Add your medication in the recommended dose: I use Seachem ParaGuard
3. OR Add aquarium salt at a rate of 1 teaspoon per gallon
4. Keep this stage for 4-7 days
5. Decrease the water temperature slowly back to normal
6. Perform a big partial water change of about 70% siphoning the substrate as much as possible

You can cure your fish from 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 is similar to ick but rarely occurs in hobby aquariums. The body of a sick fish is covered with tiny gold-colored dots (similar to gold dust). This disease is highly contagious and can quickly spread to all your fish.

Velvet is difficult to be noticed in the early stage because the dots are so small. Usually, fish keepers realize too late that something is wrong when the skin of the fish starting to peel off and fish start bleeding.

How to cure velvet:

• If discovered early, velvet can be cured with copper medication (I had great success with Seachem Cupramin)
• For best results, turn off the lights on your aquarium until the disease is completely cured
• Perform 70-90% water changes once your fish are symptom-free

Important: copper medication is deadly to shrimps and snails, so be careful with it. Also note, that once you apply copper to a tank, you can’t keep shrimps and snails in that tank anymore. Copper can’t be washed out from a tank. Be careful with it!

Fin, Tail Rot

Rotting fins and tail is a bacterial infection in guppies. It can also be caused by a fungus that grows on the nipped fins. Usually the fins and tail of the sick fish look like it is stuck together. Poor water quality and ammonia burns can also cause rotting tails.

It is important to know what causes the rotting fin because bacterial infection and fungus are treated in a different fashion.

If the fins and tail do not have any damage but have an obvious sign that is started rotting, most likely it is caused by bacteria.

If the fins or tail is damaged and started rotting, most likely it is a fungus that causes the problem.

How to cure fin, tail rot:

• Separate the sick fish to a hospital / quarantine tank
• In case of bacterial infection treated with antibiotics such as Maracyn, Maracyn 2, Tetracycline or Seachem ParaGuard
• If fin rot is caused by a fungus, treat with special medication – always follow instructions
• In case of “ammonia burns”, provide your fish with high-quality water

I highly recommend treating your sick fish in a separate tank, because you don’t want to apply antibiotics or medication to healthy fish.

Guppy Disease (Protozoan)

Protozoan is a tiny parasite that affects mainly guppies. It can be also harmful to other fish, but guppies are the most common that gets infected by this parasite.

The parasite attaches to the fish’s skin and slowly enters the fish body through their muscle until reaches the bloodstream.

This parasite usually develops in unheated tanks along with bad water quality.

How to treat protozoan:

• Add a heater to your aquarium and keep a stable water temperature
• In early-stage Malachite Green or Formalin can cure this disease
• In more advanced stages, copper medicine such as Seachem Cupramine should be used
• After treatment, perform 50-70% partial water change

You can prevent protozoan guppy diseases by heating the aquarium water and doing regular partial water changes.

Columnaris & Mouth Fungus

Although it looks like a fungus, this infection is actually caused by bacteria. The bacteria colony is usually formed on the fish’s mouth or middle area of the body as a big white splash. The sick fish have trouble swimming because the infection slowly paralyzes the muscle. They also lose their appetite.

The bacteria is highly contagious and mostly affects female guppies; however male guppies can also be infected if the illness is not treated. It can wipe out the whole fish colony in a tank.

How to treat Columnaris and mouth fungus:

• The key to successfully cure Columnaris is to start the treatment as soon as you see the first symptoms
• You can use Maracyn antibiotic or Formalin (which is a strong chemical) to cure this 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 big 50-70% water change.
• A 30 minutes potassium permanganate (KMnO4) bath can also cure Columnaris. Use this treatment carefully. Potassium permanganate is a powerful oxidizing agent and you should not exceed 10mg/l in the bath, because it can burn your fish.

Avoid over-crowding your fish, perform regular water changes, add adequate filtration and ensure good water movement and aeration in your tank in order to prevent Columnaris disease and mouth fungus.

Dropsy

Dropsy is caused by a bacterial infection that typically targets the liver or kidneys, leading to fluid accumulation in the abdomen that the fish cannot expel. As a result, the fish may appear swollen, discolored, and sometimes distorted. Its scales stand out like pine cones, raised from the body.

The belly becomes bloated, impairing the fish’s ability to swim. This bloating can also result from fluid buildup in the colonic cavity due to factors such as water pollution, genetic disorders, or diet.

Overfeeding blood worms or prolonged high stress can also induce dropsy.

How to Treat Dropsy:

• Unfortunately, dropsy caused by a bacterial infection can not be treated, because the bacteria cause damage in the fish’s internal organs. By the time the fish presents any symptoms, their damage is so big that there is no return.
• If the swollen belly is not caused by bacterial infection, there are things you can do: provide the right water parameters and feed a variety of good food.

Some guppy fish keepers reported, that Epsom salt can slow down this disease, and help the fish relax, however, it won’t cure dropsy. If you want to treat your fish, you should not treat the entire aquarium, but you should give an Epsom salt bath to the sick guppies. Put 2 tablespoons of Epsom salt to 1 gallon of water, and put the fish in it for about 30-45 minutes. Make sure that the water has the same temperature as the water in your tank. The best is to use tank water for the treatment in a separate container.

You can prevent dropsy disease by ensuring good water quality and providing a variety of high-quality food.

If you want to learn more about the dropsy disease, please check out my linked article, in which I go into more details.

Swollen Gills and Gasping

Guppies and generally fish breathe by taking water through their mouth, and then releasing it through their gills. They take oxygen out from the water with their rake. Rake is similar to lungs, and it is a very sensitive organ.

Swollen gills are usually caused by ammonia or carbonate poisoning. Ammonia is a highly dangerous toxin. It is the result of decomposing fish food, organic matter and fish waste. Carbonate can be found in different rocks and substrate.

Ammonia in low quantities will burn the gills, which will become inflated. In higher quantities, ammonia is deadly.

Swollen gills also cause guppies to gasp for air at the surface of the water.

How to treat swollen gills:

• if your guppies has rapid gill movement and are gasping for air, you should immediately do a 50% water change
• also monitor water parameters during the next few days and test for ammonia
• stop feeding the fish for few days, because feeding can cause ammonia spikes
• you can also add nitrifying bacteria (you can purchase API Quick Start from Amazon)

Red Blood Spot on Guppy Stomach / Body

The red blood spots on the stomach or body of guppies can be caused by ammonia or nitrites poisoning.

This usually happens in new aquariums, which are not cycled yet. A new aquarium can take up to 6 weeks to be fully cycled.

If you introduce fish in a new aquarium, most likely the ammonia and nitrite levels will rise quickly, because there are not enough beneficial bacteria to transform these compounds into nitrates.

Ammonia, in the smallest quantity, is deadly for guppies and most fish. Nitrite is also highly toxic and will cause poisoning and serious damage in the fish.

I receive lots of emails from beginners, who just started their guppy aquarium and their fish are dying for no obvious reason. Well, ammonia and nitrites are an invisible killers.

How to treat red spots:

• Red blood spots on the belly cannot be treated, but it is possible to save the fish if the poisoning level is not too high and you take action in time

It is better to avoid ammonia poisoning than to deal with it. Please allow your aquarium to cycle for at least two weeks, better is to let it sit for 6 weeks.

If you add fish before the aquarium is cycled, use a test kit to measure ammonia, nitrite and nitrate levels (0 ppm ammonia, 0 ppm nitrite, 10-40 ppm nitrate).

Change water frequently; once a week might not be enough with a new aquarium. Measure the water parameters and change the water if you see any sign of ammonia or nitrite.

You can buy the Seachem Ammonia Alert from Amazon, to constantly monitor ammonia levels. This tool is not as precise as test kits, but it can give you a good indication on the ammonia level.

Reduce feeding or skip a day to avoid ammonia buildup.

Using live plants in your new aquarium is also really beneficial because some plants will absorb ammonia from the water.

Viral Haemorrhagic Septicaemia (VHS)

This disease is caused by a virus within the blood of the guppy fish. The first signs of viral haemorrhagic septicaemia are lesions on the body. Later ulcer and sores will develop and fins will start rotting. Pale gills and bulging eye can also be signs of VHS. The fish will eventually stop eating and become darker in color.

How to treat viral haemorrhagic septicaemia:

• Treat all your fish with antibiotic such as Maracyn 2 – API Furan 2 can help cure VHS
• Do huge water changes after treatment

Popped Eyes

Fish pop-eye can be caused by a wide range of factors, therefore 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.

How to cure pop-eye:

• It is very hard to cure because it is not obvious what is causing it
• You can start medicating your fish with different treatments, however, you might cause more harm than good

Swim Bladder Disorder

The swim bladder is an internal organ in fish, which is filled with gas and helps in controlling their buoyancy. This organ is also responsible for keeping the fish at current water depth and keep balance while swimming.

In guppies swim bladder disorder is not a very common problem but it is usually caused by high stress: moving guppies from shallow to deep water. The fish will float at an angle or upside down, unable to control the swimming and keep the balance.

Poor water parameters such as high ammonia can also cause disorders in the swim bladder.

This is a video of a sick guppy fish with swim bladder disorder:

Swim Bladder Inflammation

This problem can be spotted very easy, because the fish belly looks distend and starts swimming with the head pointing to the substrate, standing on its head.

This is caused by a virus and unfortunately cannot be cured. Fish with such symptoms should be removed from the tank and destroyed right away.

Gill Flukes, Gill Worms

A tiny white worm that can be viewed with a naked eye causes the gills of the guppy fish to bleed. The fish is constantly gasping for air at the water surface or sits at the bottom of the aquarium having a hard time breathing.

How to treat gill flukes:

• You have to treat the whole aquarium with special medication – follow instructions. I discovered in the early stage, fish with gill flukes can be saved. However, you can’t do anything for fish with bleeding gills.

Gill worms are introduced in your aquarium usually by adding new fish or plants. This is why is important to keep newly purchased fish in quarantine. Bad water quality will also encourage the spread of gill flukes to other fish.

Camallanus Internal Worm

Camallanus is one of the most commonly found parasites in guppies. This parasite can reach up to 0.8 inches in length and is sticking out from the anus of the fish. It is easy to distinguish from wish waste because the Camallanus has a brown or orange color and has a movement similar to worms.

Occasionally other fishes attack the Camallanus, which is sticking out.

There is no such proof of where the parasite is coming from. Fish breeders reported that these parasites are mostly found in guppies that are kept outdoor in ponds and fed with live Cyclops.

How to cure Camallanus parasite:

• Camallanus is usually treated with Levamisole (commonly known as Ergamisol) for at least 5 days, but Fenbendazole and Parcide X or D works as well.
• Perform substrate vacuuming, complete filter cleaning after
• Do huge water changes: 70-90%
• After 3 weeks repeat the Levamisole treatment, clean filter and vacuum the substrate again

Avoid feeding live Cyclops to your guppy fish in order to avoid this nasty parasite.

Hexamitiasis – Hole in the Head or Body

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Hexamitiasis is caused by a protozoan parasite, Hexamitia. This parasitic disease is rare in guppies. However, there are guppy fish keepers who struggle with this disease.

Guppies infected with Hexamitia produce white, stringy feces and their colors become pale. The infected guppy will lose its appetite and eventually will refuse to eat.

In other fish species such as cichlids, one ore multiple holes will appear on their head. In guppies, these lesions appear on their body.

How to cure Hexamitiasis:

• Hexamitiasis is usually treated with metronidazole (commercially 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 in available at most pet shops, however, in other countries, it can be purchased with a veterinary prescription

Hexamitiasis usually appears in overstocked aquariums, where the filtration is not adequate. The lack of oxygen and water changes can also be a factor of Hexamitiasis.

I highly recommend oxygenating the water, setting up proper filtration and doing weekly water changes in order to avoid this disease.

Bent Spine (Scoliosis)

Scoliosis, commonly known as crooked back or bent spine in guppies isn’t rare. It is usually a result of genetics and environmental factors.

Typically you will find this disease or anomaly in younger fish. In some guppy fry the scoliosis can be observed only from above, while in others the side view will reveal the bent spine.

Usually guppies with crooked back will have trouble swimming.

Scoliosis is typically caused by in-breeding guppies and it is specific to live bearing fish. The result of scoliosis is slower growth and swimming problems.

Guppy fish with bent spine are usually weaker and often they get bullied by the others. They also have a shorter lifespan.

Reproduction of guppies with crooked back is possible, though is not recommended. Because this health issue is a result of genetics, the parents will pass it to the offspring.

I’ve experienced a bent spine female guppy giving birth to 45 fry. About 90% of the fry had bent spine. So it is very likely that most of guppy fry will inherit this health condition.

How to treat Scoliosis:

• unfortunately there is no cure to bent spine
• it is not contagious; however it can be inherited by offspring

Guppies with this disability can still live a good life, if you give them a good diet and good water conditions.

Fish Tuberculosis

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

The fish becomes inactive and slowly dies. Tuberculosis can be passed to other fish if they consume the dead body of the sick fish. This disease can also be passed to the offspring.

Tuberculosis in fish cannot be treated easily. Dead fish should be removed from the tank immediately. Fish that are presenting symptoms should be quarantined and treated with Neomycin, Kanamycin or Isoniazid antibiotics. If there is no improvement, sick fish should be euthanized to avoid the spread of infection.

I’ve written a whole article about how to euthanize guppy fish in the most human way. I highly recommend reading it, if you are dealing with sick fish, that cannot be treated anymore.

In very rare cases this disease can also be passed to humans. So be very careful when dealing with sick fish.

Applying Treatments to Your Fish Tank

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. Once the medication is over, you can place it back.

Always read the labels on the medication and follow instructions. Never overdose on the treatment, because you can cause more damage to your already sick and healthy fish.

After medicating your fish, perform big water changes to eliminate the medicine from the water.

Conclusion

I really hope this article has helped you to figure out the disease and treatment for your guppy fish.

When keeping fish, is important to check your fish daily and ensure you react fast to any illness. Discovering diseases early is the key in saving your fish from death.

Always have medication on hand, or at least know where to go when you need them.

If you have any questions regarding this content, please let me know in the comments below.

Resources:

• Featured Photo: https://www.flickr.com/photos/f_jean/5502760684
• Dropsy  Photo: https://www.flickr.com/photos/f_jean/5502168559/