Guppy Diseases: 16 Life-Threatening Illnesses & Their Cures

Last Updated: March 22, 2023 by Dave Gibbins

Fish owners love keeping guppies because they are hardy fish. Compared to other species, these tropical fish rarely get sick and can tolerate different water parameters.

Rarely, but still…

Guppies are generally healthy fish and suffer from only a few diseases. Guppy diseases are usually caused by parasites, bacteria, or viruses. Fortunately, a proper aquarium setup can help prevent them. 

We will discuss different guppy diseases, their symptoms, and preventive and treatment measures. Keep reading. 

Common Guppy Fish Diseases – Detailed Guide

Here is a detailed guide on 16 guppy diseases. 

1. White Spot Disease/Ich

The white spot disease or ich is a common disease among guppies. Ich is a parasitic disease caused by Ichthyophthirius Multifilis. Your fish will have white spots on their fins and skin because these parasites create cysts on the skin. These cysts then mature, fall off, and develop into new parasites and the cycle continues. 

Poor water quality with fluctuating temperatures and mismatched pH promotes the growth of parasites and protozoa. This makes your fish prone to white spot disease. 

The most common symptoms include loss of appetite. Your ever-hungry guppies will no longer seem interested during feeds. They will also be less energetic. Sick guppies also appear uncomfortable and constantly rub their bodies against surfaces in the tank, including decorations and rocks. 

Since the symptoms are easy to detect, this disease is rarely fatal to guppies. This is what you should do to cure ich.

How To Treat White Spots

Here are four steps to cure white spots disease.

• Increase Temperature To 80 Degrees

Maintaining the tank temperature on the higher end will speed up the life cycle of the ich. Nevertheless, increase the water temperature slowly, preferably one degree a day. 

• Use Medication

Additionally, use medication to control the parasite as your vet prescribes. Malachite Green and Formalin have proved effective at treating ich. 

• Add Aquarium Salt

Add one teaspoonful of aquarium salt for every gallon of water for 4-7 days.  Remember to add salt to both the hospital tank and the main tank. 

• Perform Bigger Water Changes

Since the tank is infected, performing a bigger water change (70%) often can help cure white spot disease. Also, vacuum as much substrate since this is where the new parasitic eggs develop. 

How To Prevent Ich

You can prevent the white spot disease by maintaining consistent water temperature and pH and cleaning the tank regularly. 

2. Fin And Tail Rot

Fin or tail rot is one of the common guppy diseases. The disease is caused by either a fungus or bacterial infection. Fish with injuries from fights are more prone to the fungus and bacteria since they latch on these wounds. Additionally, ammonia burns and dirty aquarium water can cause rotting tails.

Administer treatment depending on the cause of tail and fin rot. The fish fins and tail may appear torn, ragged, stuck together, missing, or have white edges or red stripes. There may also be clotted blood on the fins’ edges or discolored fins and tails.

How To Treat Fin Or Tail Rot

Follow the following steps to treat the affected fish:

• Move the sick fish immediately into a separate tank to prevent new infections. 
• Use antibiotics for bacterial infection. Guppies with a bacterial infection have rotting fins and tails without evident damage. 
• Use special medication to treat fungus infection and follow the provided instructions. A fungal infection is characterized by evident damage and fin rotting. 
• Ensure the tank has high-quality water if the rotting is a result of ammonia burns.
• Help the fish relax and de-stress with bathing techniques.

How To Prevent Fin Or Tail Rot

To prevent tail and fin rot, avoid housing these peaceful fish with aggressive fish. Some of the species to keep off are barb fish, bettas, angel fish, and gourami. Furthermore, avoid overcrowding the tank and practice good tank habits. 

Excessive fin nipping creates injuries that harbor bacteria and fungus.

Factoid: Find out more about guppy fin rot — Guppy Fin Rot: Main Causes & Symptoms And Quick Prevention

3. Swollen Gills

Guppies breathe by taking water in their mouth and passing it through the gills so the rake can take the oxygen out. The rake is a sensitive organ that functions as the human lungs. 

If the tank water has high ammonia levels, these can affect the fish’s gills. Ammonia is a highly toxic chemical produced by decomposing fish food, fish waste, dead fish, and organic matter. 

Low levels of ammonia can burn and inflate the gills. This is why guppies with swollen gills gasp for air. Ammonia is deadly in higher amounts.

How To Treat Swollen Gills

If your guppies are gasping for air, do the following:

• Perform a 50% water change. This will dilute ammonia levels in the fish aquarium.
• Stop daily feeds for a few days to control ammonia buildup. 
• Test ammonia levels for the next five days.
• Add nitrifying bacteria.

4. Swim Bladder Disorder

Guppies, like other fish, have a swim bladder that helps with buoyancy. This organ is filled with gas to maintain balance and water depth when swimming. 

This rare guppy disease is caused by stress, overeating, or low water temperature. Other causes include physical injuries, shock, pregnancy, and parasitic and bacterial infections.

Guppies with swim bladder disorder have the following symptoms:

• Difficulty maintaining balance
• Swimming problems
• Swimming at a strange angle or upside down
• Decreased appetite
• Lethargy
• Clamped fins

How To Treat Swim Bladder Disorder

We recommend you find out what factors may be stressing your guppy and eliminate them. In addition, test that the water has low ammonia levels and perform 70% water changes. Moreover, maintain the tank temperature at 78 to 80 degrees F. 

5. Columnaris & Mouth Fungus

This deadly infectious fish disease mimics a fungal infection, but it is a bacterial infection. Stress, improper diet, and the introduction of bacteria are the main causes of this guppy disease. 

The fish’s mouth gives you the first signs of the infection. A bacteria colony forms a big, cloudy splotch in the mouth or the middle part of the fish body.

The highly contagious bacterium can kill your whole fish colony, and it largely affects female guppies. It can rarely affect males, but male guppies will not be safe if you do not take steps to contain it. 

Other signs of columnaris & mouth fungus are decreased appetite and difficulty swimming. The infected fish find swimming impossible since the disease paralyzes the muscle. 

How To Treat Columnaris & Mouth Fungus

This infection is treatable when detected at an early stage. You can:

• Use a strong chemical, preferably prescribed by your vet, to cure the infection. The majority of fish keepers swear Formalin helps. 
• Add aquarium salt to the fish tank. We recommend 3 tsp for 1 gallon of water daily for three days. 
• Include a 30-minute medicine bath.
• Provide sufficient minerals.
• Maintain regular tank maintenance and perform water changes. 

How to Prevent Columnaris & Mouth Fungus

The best preventative measure includes keeping the right number of guppies for your tank. Even then, ensure there is adequate filtration, make regular water changes, and aerate the water. 

6. Velvet (Oodinium)

Velvet disease is not one of the common guppy fish diseases. Guppies with velvet disease have tiny dots that look like gold dust that is practically impossible to spot in the early stages. This guppy disease is highly contagious and only becomes evident when it is too late. 

Velvet is caused by oodinium, a parasite that is present in most aquariums. 

The parasite enters a fish’s system through the skin, gills, and fins and devours the nutrients inside the cells. It then matures and reproduces more parasites that are released into the water. 

The parasite mainly affects stressed guppies that live in a poorly maintained tank. Symptoms include:

• Guppies rubbing their bodies against hard surfaces
• Loss of appetite
• Weight loss
• Gold dust and velvety skin
• Rapid breathing
• Lethargy 
• Skin peels off

How To Cure Velvet

One way to cure velvet is by turning off the lights to promote fast healing. Ensure the tank stays dark until your guppy fish is completely cured. In addition, make frequent water changes to do away with nagging parasites. We recommend a 70-90% water change. Lastly, use copper medication. Copper is effective in curing velvet disease. 

NOTE: Copper treatment is fatal to snails and shrimp. Once you introduce copper into a fish tank, it will never become home to snails and shrimp.

How To Prevent Velvet Disease In Guppy Fish

You can prevent velvet by performing regular water changes and water testing. Make sure the pH levels, degree of water hardness, and temperatures are in an optimal range. Also, avoid overcrowding the fish tank. 

7. Popped Eyes

Popped eyes are among the hard-to-treat guppy diseases. It is caused by different factors, including injury, poor water quality, dropsy, bacterial infection, tuberculosis, fungus, and internal parasites. 

Fish pop-eye is characterized by cloudy or discolored eyes. The eyes may also swell or have leaking fluid. Though not fatal, pop-eye may lead to blindness. 

How To Treat Popped Eyes

There are several causes of popped eyes, and pinning the correct cause can be challenging. This makes it difficult to treat, and administering different medications can hurt your sick fish.  

Nevertheless, isolate the sick guppy fish in a hospital tank and ask your vet for directions. 

8. Red Blood Spot

The red blood spot is easy to identify on the guppy’s stomach or body. The condition manifests in new aquariums that are not fully cycled.

When you introduce fish to a tank without beneficial bacteria, their waste will lead to a buildup of ammonia and nitrites. These toxic compounds then cause poisoning, damage, and death, even in tiny amounts.  

The red spots are a sign of ammonia poisoning. This should be a wake-up call that your aquarium is not a healthy environment.

How To Prevent Red Blood Spot

You can avoid ammonia poisoning by cycling the aquarium for two weeks. Next, allow the beneficial bacteria to grow for 6-8 weeks. Before you introduce fish, test to confirm that the ammonia and nitrite levels are 0 ppm.

9. Camallanus Internal Worm

Outdoor guppies and those that feed on live cyclops are mainly affected by the Camallanus worm. It is a parasite that latches to the anus of the guppy and has brown or orange coloration. The worm can reach ¾ an inch and never leaves the fish. 

How To Treat Camallanus Internal Worm

You can treat your sick fish by giving them Levamisole or any other medication prescribed by your vet. Once the treatment period is over, perform filter cleaning, substrate vacuuming, and a 70-90% water change. Repeat this process after three weeks. 

10. Viral Hemorrhagic Septicemia (VHS)

This is another deadly infectious fish disease caused by a virus. VHS is also called red pest since the infected fish have red streaks on their body. Symptoms include:

• Lesions
• Sores
• Ulcers
• Rotting fins
• Pale gills
• Bulging eyes
• Pale body-color
• No appetite 

The virus travels through the blood, causing damage to the circulatory system, including the heart and blood vessels. It can also cause internal bleeding and death. 

How To Treat VHS

Maracyn is the only proven effective antibiotic for VHS. Treat your tank and fish with it, and perform a 70% water change after the treatment period. 

11. Scoliosis (Bent Spine)

Scoliosis is a rare condition, but it does affect guppies. The disease may either be due to genetics or environmental conditions. In-breeding livebearer fish like guppies often results in a bent spine.

Fortunately, this disease is not contagious but inherited from parents. This is why you can observe a bent spine in guppy fry from a side view or above. 

The sick fish have difficulty swimming. They also have a weaker immune system and are subject to bullying. 

How To Treat Bent Spine

There is not much you can do except provide the sick fish with a healthy diet and practice good tank habits.  They generally have a shorter lifespan.

12. Fish Tuberculosis

Fish TB is a contagious disease caused by mycobacterium Marinum. Guppies living in tanks with high waste buildup, low oxygen levels, and irregular water changes are more susceptible to tuberculosis since these bacteria thrive in such conditions. 

 Fish tuberculosis is easily transmitted to other fish. Symptoms include: 

• Hollow belly
• Tail and fin rot
• Loss of appetite
• Body discoloration
• Bulging eyes
• Lesions
• Bent spine

This YouTube video explains more about Fish Tuberculosis:

How To Treat Tuberculosis

The following steps are more inclined towards controlling the disease rather than treating it.

• Move the sick fish into a quarantine tank.
• Remove any dead fish since the healthy guppies can get infected from feeding on them.
• Provide antibiotics for the infected fish. You could use Neomycin, Kanamycin, Isoniazid, or other prescribed medication.
• Euthanize the sick fish if there is no improvement. This will ease their pain and suffering. 

Did you know humans can get infected by fish tuberculosis? Therefore, always wear hand gloves when handling sick fish. 

13. Hexamitiasis

This rare guppy disease is common in overstocked tanks with poor filtration, inadequate water changes, and low oxygen levels. Hexamitiasis is a parasitic disease caused by protozoa. 

Symptoms of this disease include white and stringy waste, pale bodies, destroyed fins, holes in the body, and refusal to feed. The fish waste can infect your whole fish colony. 

How To Treat Hexamitiasis

• Move the sick fish into a quarantine tank.
• Add metronidazole (Flagyl) to your fish’s food. This medication is available in most local pet stores.
• If your guppies are not eating, add the treatment to the water. 

To prevent Hexamitiasis in your freshwater fish, avoid overcrowding and clean the tank regularly. 

14. Gill Flukes

Gill flukes, gill worms, or gill disease is another common guppy disease. It is caused by a tiny, white worm that attacks the fish’s gills. If you pay close attention, you may spot the gill worms. 

Gill worms are brought about by poor water quality and the introduction of infected new fish or live aquarium plants. 

To prevent gill flukes, you should always quarantine new fish to ensure they are healthy before adding them to the main tank. 

Fish suffering from gill flukes have difficulty breathing and may stay at the bottom of the tank gasping for air. 

How To Treat Gill Flukes

This condition is treatable in the early stages with special medication. Ask your vet for a prescription and follow all the directions. 

However, treatment is impossible if your fish’s gills have started bleeding. In this case, your guppies will bleed to death. 

15. Dropsy 

Dropsy disease is caused by bacteria that affect the liver or kidney. The disease is a result of a buildup of excess fluids in the tissues and body cavity of the fish. Guppies have trouble swimming when their abdomens are bloated. 

Improper feeding, water pollution, and genetics can cause dropsy. If your guppies are constantly stressed or eating a lot of bloodworms, they are also prone to getting sick. 

The common symptoms of dropsy are:

• A swollen body
• Raised scales that resemble spine clones
• Bulging and sunken eyes
• Pale gills
• Red and swollen anus
• Lethargy and loss of appetite

Sadly, dropsy is a fatal disease because it only becomes evident after the bacteria has caused severe damage to the guppy’s internal organs. Nevertheless, you can slow the disease by:

• Moving the sick fish to a quarantine tank. The disease is infectious, especially to fish with a weak immune system. 
• Preparing an Epsom salt bath to help guppies relax. 

How To Prevent Dropsy

The best way to prevent dropsy is to ensure the tank water is always clean. Also, avoid keeping your guppies in a stressful environment for long and feed them high-quality food. 

Factoid: Dropsy is one aquatic illness that literally “kills off” your pet fish in a painful way. Know more about this deadly bacterial attack by reading our article on Guppy Dropsy: Early Detection And Fast Fix For Your Pet Fish for tips, hints, and first aid ideas.

16. Swim Bladder Inflammation

Swim bladder inflammation has similar symptoms as Swim Bladder Disorder. Your guppy fish start to swim at strange angles. Moreover, the belly will appear inflamed and swollen as a result of a viral infection. 

How To Treat Swim Bladder Infection

This disease is highly infectious and has no treatment. So once you notice a sick guppy, remove it from the tank to prevent further infections. 

6 Helpful Tips to Prevent Guppy Diseases

Indeed, guppies are hardy fish. The majority of the above guppy diseases are preventable if you practice the following. 

Maintain Water Quality

If your fish aquarium has good water quality, your guppies will lead a healthy and long life. An unmaintained tank stresses the fish and makes them prone to infections and diseases. 

Feed Appropriate Portions

Also, feed your fish the required amount of food. Overfeeding can cause health problems later and promote toxic ammonia build-up. 

Practice Good Maintenance Habits

Maintain your aquarium by performing weekly water changes. Doing so promotes a healthy environment for your guppies.

Inspect Your Fish

Make sure you visually inspect your fish daily. If you notice any sick fish, immediately place them in a quarantine tank to prevent more infections. Also, get rid of any dead guppies. 

Quarantine New Fish And Decorations

When buying new fish or tank decorations, make sure you quarantine them for up to four weeks. During this time, check whether the new fish have parasites or symptoms of guppy diseases. 

Reduce Stress

Stress can easily kill your guppies. Stressed guppies have a weaker immune system that is vulnerable to any bacteria, parasites, or viruses in the tank. 

However, you can reduce guppy stress by adding adequate hiding places. This will provide a sense of comfort, security, and privacy. In addition, maintain the correct water temperature. 

Add an aquarium heater to stabilize the temperature if you do not live in the tropics.

Moreover, maintaining water quality can prevent stress in guppies. When performing water changes, ensure that the added water has a similar temperature, pH, and hardness to match the aquarium. 

Lastly, keep your guppies with other peaceful fish. 

Conclusion

Some guppy diseases are common, while others are rare. Some are preventable and curable, while others are highly infectious and deadly. 

Regardless, guppies are affected by only a few diseases and can stay healthy if their optimal tank conditions are met. We recommend that you take preventative measures instead of treating sick guppies.