Last Updated on December 31, 2019 by Cooper Fulton

Pond Fish Diseases

Pond owners often lose their precious fish to diseases which remain undetected. Pond Fish diseases are often caused due to a variety of reasons that can be easily prevented.

The pond owners should keep a regular check on their pond to ensure their fish are healthy. The most common disease-causing factor is poor water quality. 

Ponds that have poor water quality have an increased amount of pathogens in them. 

The water contains fewer nutrients and oxygen which weakens a fish’s immune system. 

Such pond fish fall sick to various bacterial and parasitic infections. 

Symptoms of Sick Pond Fish

Pond owners should observe their fish for these symptoms to identify fish disease.

Risky Behaviour – Some fish tend to rise to the surface and make themselves easily accessible to prey. Others change their usual behavior patterns and start staying at the bottom of the pond. 

Breathing Difficulties – Some diseases make it difficult for the fish to breathe. In such cases, the fish gulp air above the water surface or breathe heavily. 

Visible Spots – Certain infections cause spots and lesions on the fish’s skin. Pond owners should check their fish’s body for these physical signs of disease.

Physical Changes – Some fish diseases cause the pond fish to lose their appetite. The fish drop weight and also become lethargic. 

General Advice for Infected Pond Fish

Quarantine – Infected or diseased fish should be removed from the pond immediately. These fish should be quarantined to avoid the spread of infection.

Medication – Diseased fish should be treated with proper medication. The dosage should be given according to the instructions on the medication. 

Pond Fish Diseases

Pond fish are vulnerable to different diseases as they are exposed to the elements. Pond fish need the right amount of nutrients and good water quality to remain healthy. 

Ponds that have poor water quality or are not well-maintained can become a risk to a fish. 

In such ponds, the presence of bacteria and parasites will be more while the nutrients will be less. 

This creates an imbalance in the pond’s environment which weakens the fish’s immunity. Pond fish, if kept in such environment will fall sick and often lose their lives if left untreated. 

To avoid such situations the pond owners should keep their pond well-maintained.

Some common diseases which affect the popular pond fish varieties are;

Grass Carp Diseases

Grass Carp Diseases

The Glass Carp are excellent swimmers who feed on aquatic plants and roots. 

These fish are dubbed as “eating machines” as they eat without a break. Due to this rapid eating, the fish sometimes grow too big for the pond. 

Pond owners should also ensure that the Grass Carp does not clear out the entire vegetation in the pond. 

The Glass Carp fish are prone to both viral and bacterial diseases. The most common among them are;

Hemorrhagic Disease – This is the most serious infectious disease in Grass Carp as it mostly ends with the death of the fish. The fish exhibit signs of internal and external hemorrhages, or the loss of blood. This disease gets transmitted through water and parasite bite.


Bacterial Gill Rot – This bacterial infection causes the fish’s head to turn dark red in color. Its gills become pale, rotted and the exposed cartilage gets covered with slime.

Treatment – Bleaching the pond water.

Enteritis – This is a high mortality disease that affects 1 to 2 yearling Grass Carp. The intestines turn purplish-red and the capillaries become congested and decay. The fish’s anal opening also becomes swollen and turns red.

Treatment – Sulfaguanidine mixed with food in a floatable pellet.

Fathead Minnow Diseases

Fathead Minnow Diseases

These fishes are often ignored as they are considered to be “baitfish”. The Fathead Minnows are used to test the water’s biotoxicity levels. 

Most Fathead Minnows have parasites or infections due to poor care. 

These fish are naturally very resilient and are not prone to diseases. 

A common infection that is seen in Fathead Minnow is Metacercariae or grubs.

Grubs – This infection affects the Fathead Minnow’s kidneys, ovaries, and liver. The presence of a large number of white grubs can result in death.

Treatment – There is no FDA approved treatment for white grubs. The infection should be stopped from spreading by isolating the infected fish. Removing snails and preventing birds from visiting the pond help to prevent grubs.

Golden Rudd Diseases

Golden Rudd Diseases

These fish are also called Rosette Pond Fish. These fish are unique as they have a silver/pink body and gold/red fins. 

The Golden Rudd is a hardy fish species and can get ill easily. 

These fish need a deep pond to hibernate and clean flowing water to remain healthy. 

The Golden Rudd needs a clean environment to flourish as it gets affected by mold and carp louse. 

Some common fish diseases that also affect the Golden Rudd are;

Black Spot Disease – This is a common pond fish disease which is caused by flatworm larvae. The affected fish develop black spots on their fins, skin, and flesh.

Treatment – Giving the infected fish a formalin bath and keeping them in quarantine helps.

Acute Hexamitiasis – This disease is caused by a parasite, H.Salmonis which is safely harbored by many fish species. 

Acute Hexamitiasis is developed when the environmental conditions are altered. 

A change in the diet or temperature causes the disease the infected fish have a high mortality rate. This disease causes inflammation in the intestine and gallbladder.

Treatment – Mixing Flagyl in fish food or in a bath is the best treatment option.

Stickleback Diseases

Stickleback Diseases

The Stickleback fish is a great addition in any pond. 

These fish are very aggressive during the breeding season. 

This species is an undemanding species and can survive in polluted water. The Stickleback fish can coexist with other species. 

The pond owner has to ensure that his pond is large enough. 

Although this fish species is sturdy, it is susceptible to diseases from parasites. Here are some diseases that affect Sticklebacks;

Tapeworm – Tapeworm is a parasite that gets passed to the Stickleback fish through the food chain. 

Some types of tapeworm like the Schistocephalus solidus change the fish’s behavior. 

Stickleback fish which have been infected with this tapeworm often behave carelessly. They remain in open waters for a long time making them easy prey for birds.

Treatment – Using Biltricide and Niclocide helps in controlling the infection. You can also use Infection Remedy which in my opining is easier and better to use.

Fin Rot – Fin Rot is a bacterial infection that commonly affects all varieties of pond fish. This disease makes the fish lethargic and causes discoloration. Fin Rot causes the tail and fins to rot away and if left untreated might be fatal for the fish.

Treatment – Melafix and Aquarisol can be added to the water to kill harmful bacteria.

White Spots (Ich) – This is a contagious parasitic disease that affects fish that live at the bottom. The parasite attaches and moves under the skin of the fish. 

It feeds on fish cells and body fluids for survival. Infected fish or pond equipment and sudden changes in the pond environment are triggers. 

White Spot disease makes the fish disoriented and makes them swim close to the surface. 

The infected fish also rub themselves against stones. 

White cysts in the size of a grain of salt start to appear in the later stages of this disease.

Treatment – Zinc-free Malachite should be used according to the correct dosage. Quarantine the infected fish to stop the spread of the disease.

Goldfish Diseases

Goldfish Diseases

The most popular ornamental fish have to be the goldfish , they are seen in many aquariums and ponds. 

They prefer to live in shaded areas of the pond. Goldfish need good water quality and aquatic plants to nibble on to survive in the pond. 

These fish need to be protected from herons and cats. Some common diseases that strike Goldfish are;

Flukes – This is one of the most common parasites found on a goldfish. These parasites hang onto the skin of the fish and feed on its slime coat. 

This makes the Goldfish bleed to its death. Goldfish which are suffering from Flukes often rub against the walls or floor. 

They may also become very thin and have trouble breathing.

Treatment – Use anti-parasite medication to prevent Flukes from harming your fish. Quarantine new fish before adding them to your pond.

Anchor Worm – This is a common Goldfish disease that infects the fish in the fall season. This is a very contagious fish disease that can easily infect all your fish. 

Goldfish which have been infected with Anchor Worm tend to scratch themselves. 

The actual worm starts to stick out from the Goldfish’s body. If left untreated the wound gets infected and kills the fish.

Treatment – Worms need to be removed from the Goldfish’s body with tweezers. 

The wound needs to be cleaned with hydrogen peroxide to prevent infection. 

Cyromazine is an effective anti-Anchor Worm medication.

Archerfish Diseases

Archerfish Diseases

These fish are quite expensive because of their unique traits. The Archerfish preys on small insects by spraying them with water droplets. 

These fish are feed on small insects from the water surface and often leap out of the pond to catch their prey. 

The Archerfish is a rare species that mixes well with other fish in the pond. 

These fish are affected by common bacterial and parasitic diseases like;

Dropsy – This is a bacterial infection which is caused by malnutrition. 

Archerfish infected with Dropsy tend to be bloated and have visibly raised scales. 

These symptoms prevent infected fish from feeding.

Treatment – Dropsy can be naturally treated by improving the water quality in the pond.

Ide(Orfe) Diseases

Ide(Orfe) Diseases

The Ide fish are ideal for deep, large ponds as they are school-fish. 

This species needs to be kept with a group of at least 5 specimens to ensure its well-being. 

The Ide fish hibernate in winter and do not feed on aquatic plants. 

These fish are popular among pond owners as they like to swim near the surface. 

These fish brighten up the look of the pond. The Ide fish is also popular for being sturdy and do not get diseases from parasites. 

These fish do need good water quality to maintain their health. Diseases which affect the Ide fish in the pond are;

Carp Virus – This virus usually strikes the Ide fish in the spring season as water and temperature change. 

The carp virus is highly contagious and can spread around the pond if it is left untreated. 

This virus can cause abdominal swelling, skin lesions, and hemorrhage.

Treatment – Quarantine the sick fish to prevent the virus from spreading.

Provide a high-protein diet along with good quality water at the right temperature.

Koi Carp Diseases

Koi Carp Diseases

Koi fish and Goldfish are popular pets for pond owners as they are not only beautiful but are resilient too. 

These fish do not fall ill easily and have a lifespan of 30 years. 

Koi fish which have ideal pond conditions rarely get sick. Pond owners should check their Koi for unusual behavior, loss of appetite and weight. 

These factors along with visible white spots or bad fins are indicators of Koi disease. 

Koi fish get sick when they get stressed due to unfavorable pond conditions. 

The common fish diseases that Koi fish are susceptible to in poor pond environment are;

Chilodonella – This Koi fish disease is caused by microscopic parasites. 

Sick Koi fish become lethargic and prefer to sit at the bottom of the pond. 

A white film covers the fish body and makes it difficult for the Koi to breathe. 

Koi fish which are breathing heavily or are gasping for air should be checked and treated. 

Treatment – Quarantine the affected Koi fish to prevent further infections. 

Check your pond water’s toxicity levels and ensure good water quality. 

Treat the infected Koi fish with a good broad-spectrum fish medication.

Fish Lice – The carp louse is a parasite that causes fish lice disease in Koi fish. 

These parasites dig into the fish’s flesh and drink its blood. 

Infected fish lose weight and the wounds become inflamed and infected. 

Infected Koi also display unusual behavior, reduced feeding, and increased mucus production.

Treatment – Visible fish lice can be removed from the infected Koi with tweezers. 

Diflubenzuron is an effective medication for fish lice in the adult and larval stages.

Peppered Corydoras Diseases

Peppered Corydoras Diseases

The Peppered Corydoras are a catfish species that do well in groups. Pond owners often choose these fish as they are peaceful and resilient. 

These fish eat food off the bottom of the pond and help to keep it clean. 

The Peppered Corydoras also need easy access to the water surface to take in air. Pond owners should also ensure that they do not use sharp substrate as it will harm this species. 

Although these catfish are a resilient species, they often get diseases due to stress. 

Poor water quality, temperature change, and decaying matter are some causes of stress. 

Red Blotch Disease – This disease widely affects bottom feeders in the pond or aquarium. 

The infected fish usually display red, bloody sores on their abdomen. In some cases, the infected fish have visible dead, white skin and blisters. 

Red Blotch disease can cause death if it is left untreated.

Treatment – A broad-spectrum antibiotic is an effective medicine. 

The infected fish should be put in quarantine and treated to stop the disease from spreading. 

Poor water quality and improper water temperature are also factors that cause disease. 

Pond owners should provide a proper environment for their Peppered Corydoras to keep them healthy.

Pumpkinseed Fish Diseases

Pumpkinseed Fish Diseases

These fish are popular among young fishing enthusiasts as they are quick to bite. Pond owners often introduce the Pumpkinseed fish to add some drama to the water. 

These fish like to be the shallow water and remain clearly visible in the pond. These fish thrive in groups and feed at all water levels in the pond. 

The Pumpkinfish need good quality water and good vegetation cover. 

A common disease that affects Pumpkinseed Fish is Heterosporis.

Heterosporous – This is a parasitic disease that spreads through infected fish and contaminated water. The microscopic spores of this parasite living in the infected fish’s muscle tissue. 

They destroy the fish’s muscle tissue and causes their body to curve inwards. 

The infected Pumpkinseed fish have white spots on their muscles. 

Since the only external symptom of Heterosporis is a curved body, the pond owner should check for unusual fish behavior. 

Treatment – There is no treatment for Heterosporis in fish. 

The infected fish must be properly disposed to prevent further infections. 

Proper water filtration devices must be used to prevent bacterial and parasitic infections.

Bluegill Diseases

Bluegill Diseases

The Bluegill fish are popular among fishing enthusiasts. The Bluegill has colorful gills and a strong body that make them attractive.

Pond owners often debate on whether to introduce Bluegill to their pond or not. These fish are territorial and need a lot of space in the pond. 

The Bluegill prefer to stay in shallow waters and hide under vegetation. 

The Bluegill fish eat smaller fish and plankton in the pond. 

Some common diseases that affect the Bluegill fish are;

Viral Hemorrhagic Septicemia (VHS) – This is a viral infection that causes fatalities. 

The disease spreads through infected fish and can spread throughout the pond. 

The infected Bluegill fish often bleed from their eyes, skin, and fins. Internal bleeding is also a symptom that points to the spread of VHS. 

Treatment – Infected fish must be put in quarantine to avoid the spread of VHS. 

The pond water must be treated with anti-bacterial medication to kill the pathogens.

Red Sore Disease – This disease is caused by two different natural organisms found in the pond water. 

The Red Sore disease is usually prevalent in the spring and fall seasons. 

Infected fish display red sores and ulcers on their bodies. This disease is fatal in some cases only.

Treatment – This disease often runs its course naturally without damaging the infected fish. 

There is no specific medication for controlling this disease. 

The pond owners should use proper anti-bacterial medication to remove harmful pathogens. 

Tilapia Diseases

Tilapia Diseases

These fish are a good food source and are often grown to be harvested at a good time. Pond owners who are intent on having Tilapia should ensure that their pond is at least 2 feet deep. 

These fish can eat anything and are good for keeping the aquatic plants in check. The Tilapia fish species are generally considered to be a resilient species. 

These fish are strong and are not prone to common fish diseases. 

This low maintenance quality of the Tilapia makes them a great choice for ponds. 

The immune power of the Tilapia fish is affected by its environment. 

Sudden changes in water quality or temperature can make the fish ill. Some infections that the Tilapia can contract are:

Gill Necrosis – Tilapia fish that are in a crowded environment often suffer from Gill Necrosis. 

Sudden environmental changes due to rainfall and temperature change also promote this disease. 

Infected Tilapia have pale or yellowish-brown lesions on their skin. 

The fish’s gills get damaged and their filaments are destroyed by the bacteria.

 Pond owners should look for fish that are gasping for air and check them for infection.

Treatment – The pond’s water quality should be checked and proper filters should be used. 

The infected fish should be fed food mixed with antibodies to help them combat the disease.

Trichodina – This is a parasitical infection that turns fatal when not treated. 

The infected fish display erratic behavior and do not eat much food. 

Pond owners should check their Tilapia for weight loss, and behavior changes. 

Infected fish rub themselves against pond surfaces to remove parasites. 

This causes skin lesions and bleeding on the fish. 

If left untreated, these lesions can get infected and cause death.

Treatment – Infected Tilapia should be put in quarantine and the water quality should be tested. 

Formalin is an effective medication that helps the Talapia to fight off Trichodina. 

This medication should be given to the infected fish until all the visible signs are gone.

Tips to Prevent Diseases in Ponds

The water in ponds is abundant with different kinds of bacteria and pathogens. Pond fish, which are healthy and have strong immune systems, tend to be disease-free. 

Fish which have poor nutrition and improper environment tend to get infected. 

Pond owners should check their pond and their fishes to ensure that they remain healthy. 

Some good tips that every pond owner should follow to keep their fish healthy are, avoid overcrowding – Make sure that your pond has adequate space for all the fish. 

Introduce only those species that can get along with each. It is essential to have a good mix of different fish species to maintain a proper balance in the pond. 

Nutritious Food – All the pond fish should have access to nutritious food in the pond. The dietary requirements of all species should be met to ensure their health. 

Avoid overfeeding as this will cause a negative impact on the pond’s environment. 

I recommend purchasing Koi Vibrance fish food. It enhances the color of all your pond fish and lasts for quite a long time.

Maintain good green cover – The pond should have a good variety of aquatic plants to support the fish. The fish should have good browsing and forage options.

It is essential to provide a good hiding space for the fish to keep them healthy.

Ensure water quality – Ponds with good water quality have the essential nutrients to support fish. Pond owners should remove pollutants and decaying matter to avoid bacterial growth.

Use proper water filtration equipment – Having clean, slow-moving water in the pond is essential to avoid stagnation. 

Stagnated water often becomes a breeding ground for various bacteria and parasites. 

I recommend every pond owner a water testing kit, this will help you test for pH, ammonia, phosphate, nitrite, and nitrate.

Knowing this is essential for every pond owner, whether you’ve just begun, or have been building/maintaining ponds for years.

Remove debris – Pond owners often use water filters with pond skimmers to keep their ponds debris-free. 

Unwanted debris like fallen leaves and trash create shadows and rot in the water. This causes an imbalance and affects the natural environment of the pond. 

Rotting organic matter in the pond becoming bacteria breeding grounds. 

This puts the pond fish at risk of contracting different diseases.

Check pond visitors – Pond visitors like birds and frogs often carry harmful parasites. 

Pond owners should keep an eye out on these visitors and check their fish for the disease. 

Prepare for the seasonal changesSeasonal changes cause changes in the pond’s environment and cause bacterial growth. 

The pond fish become more susceptible to diseases in particular seasons. Pond owners should mind the seasonal changes and take precautions to keep the fish safe. 

The water temperature, oxygen levels, and nutrients should be checked. Some fish species hibernate in winter while some cannot survive harsh cold. 

The pond owners should make adequate arrangements to keep all the species healthy. 

Aquatic plants – Pond owners should have a good mix of floating, submerged and marginal plants. 

These plants are crucial to the pond as they provide essential oxygen in the water. 

The roots are also good food sources for some fish species. Aquatic plants help to maintain an ideal balanced environment in the pond.

Check fish behavior – Pond owners should check their fish for signs of unusual behavior. 

Diseased fish often lose weight, develop spots, have trouble breathing and rub themselves against pond surfaces. 

By observing for such signs, the pond owners can quickly treat the infected fish and stop the spread of the disease.