Fish Diseases – Bacterial, Viral and Parasitic

Fish diseases encompass a broad spectrum of health issues that can significantly impact the well-being, growth, and survival of various fish species. These diseases can arise from multiple types of pathogens, including bacteria, viruses, fungi, and parasites, as well as environmental stressors. Bacterial diseases, caused by organisms such as Aeromonas, Vibrio, and Edwardsiella, often manifest through symptoms like ulcers, skin lesions, and abnormal swimming behaviors. Viral diseases, including infections from the Viral Hemorrhagic Septicemia Virus (VHSV) and Infectious Hematopoietic Necrosis Virus (IHNV), can lead to severe health complications, including hemorrhaging and organ failure. Fungal diseases, such as those caused by Saprolegnia, result in conditions like “cotton wool” disease, characterized by skin lesions and the potential for secondary bacterial infections. Parasitic diseases, resulting from organisms like Ichthyophthirius (ich), Dactylogyrus (gill flukes), and Argulus (fish lice), often lead to skin damage, irritation, and noticeable behavioral changes.

The symptoms of fish diseases can vary widely and include behavioral changes such as lethargy and scraping against surfaces, along with physical signs like lesions, discoloration, and swelling. Additionally, gills and fins may appear abnormal, showcasing frayed edges or pale coloration. Various factors contribute to the development of these diseases, including environmental stressors like poor water quality, temperature fluctuations, and inadequate nutrition, which can predispose fish to infections. High infection pressure from overcrowding and the introduction of new fish into an ecosystem can further exacerbate the spread of pathogens. Furthermore, fish with compromised immune systems are more susceptible to infections, underscoring the importance of overall health management.

Diagnosing fish diseases requires careful observation of symptoms, potential pathogen identification through laboratory testing, and assessments of environmental conditions. Treatment strategies may involve medications such as antibiotics, antifungals, and antiparasitics, as well as efforts to improve water quality and implement biosecurity measures to prevent disease spread. Preventative measures, including good husbandry practices, regular health monitoring, quarantine protocols for new fish, and the maintenance of optimal environmental conditions, are crucial for avoiding disease outbreaks. Understanding fish diseases is essential not only for aquaculture and fish farming but also for conservation efforts, as these diseases can significantly affect fish health, the success of fish farming operations, and the sustainability of wild fish populations. Continuous research is necessary to develop effective treatments and management strategies to address emerging fish diseases and maintain healthy aquatic ecosystems.

Factors of Disease

The following points outline the primary factors that affect fish health:

• Water Quality Parameters: Fluctuations in water quality are pivotal in determining fish health. Key parameters include:
  • Temperature: Variations can stress fish, making them more susceptible to diseases.
  • Dissolved Oxygen Levels: Insufficient oxygen can lead to hypoxia, affecting fish respiration and overall health.
  • Carbon Dioxide (CO2): Elevated levels may result from organic decay and can be toxic to fish at high concentrations.
  • pH Levels: Extreme pH fluctuations can disrupt metabolic processes in fish.
  • Transparency and Turbidity: High turbidity levels can inhibit photosynthesis in aquatic plants, reducing oxygen production and creating an unhealthy environment.
• Pollution from Waste Products: The accumulation of organic waste in aquatic environments leads to various health issues. Waste can infect gills, skin, and mouth cavities of fish, compromising their immunity and increasing vulnerability to pathogens.
• Release of Harmful Gases: The decomposition of organic matter can generate gases such as hydrogen sulfide (H2S), ammonia, methane, and carbon dioxide. These gases can be toxic and disrupt normal physiological functions in fish.
• Contamination from Polluted Water Sources: Introduction of polluted water from sewage systems, industrial discharges, and urban runoff introduces harmful substances into aquatic ecosystems, exacerbating the likelihood of disease outbreaks.
• Agricultural Runoff: Water runoff from agricultural fields often contains fertilizers and pesticides that can harm aquatic life. This runoff can lead to eutrophication, which depletes oxygen levels in the water and encourages harmful algal blooms.
• Environmental Stressors: Stressors such as rapid temperature fluctuations and high stocking densities can compromise fish immune systems. Stress is a significant factor that can precipitate disease outbreaks, as stressed fish are less capable of resisting infections.
• Feeding Practices: Overfeeding can result in uneaten food decaying in the water, contributing to pollution. This decay not only affects water quality but also encourages the proliferation of harmful bacteria and parasites.

Symptoms of Disease

The following points delineate the common symptoms associated with fish diseases:

• Behavioral Changes: Affected fish often exhibit alterations in behavior, such as isolation from the school or group. This solitary behavior can indicate stress or illness. Additionally, differences in swimming patterns, such as lethargy or erratic movements, are noteworthy signs.
• Feeding Habits: Diseased fish may stop feeding entirely or display a significant reduction in food intake. This aversion can be a response to discomfort or illness.
• Physical Appearance: Changes in body shape and coloration can be indicators of disease. Discoloration may manifest as pale or dark patches, reflecting underlying health issues.
• Fins and Scales: Observing the edges of fins is crucial; a whitish or reddish hue, along with scale loss, can signify infections or parasites. Damage to fins can also indicate environmental stressors or pathogens.
• Fluid Accumulation: The presence of excessive fluid in the body cavity, particularly a reddish fluid at the base of fins, is a serious symptom. This condition may suggest systemic infections or organ failure.
• Gastrointestinal Distress: Symptoms such as a swollen abdomen may arise from gastrointestinal blockages or infections. In severe cases, necrosis of the gills may occur, leading to respiratory distress and excessive mucus secretion.
• Skin Lesions: The appearance of body swelling followed by spots, abrasions, or ulcers is indicative of fungal infections or bacterial diseases. The presence of furunculosis, characterized by boil-like lesions, is particularly concerning.
• Unusual Movements: Sudden, erratic movements such as jumping out of the water or rubbing against rough surfaces can indicate irritation, parasitic infections, or environmental stressors. These actions can lead to injuries or exacerbate existing conditions.
• Imbalance in Swimming: Fish may demonstrate abnormal positions while swimming, including moving in circles or exhibiting unusual orientations like tail or head down. Such behavior often points to neurological or environmental issues.
• Eye Abnormalities: Exophthalmia (bulging eyes) or enophthalmia (sunken eyes) can occur with various diseases and may impair vision, affecting a fish’s ability to navigate and feed effectively.

Examples of Diseases of Aquarium Fishes

Aquarium fishes are susceptible to various diseases that can adversely affect their health, behavior, and overall well-being. Understanding these diseases is crucial for maintaining a healthy aquatic environment. The following examples highlight different categories of diseases commonly encountered in aquarium settings, along with their causative agents, symptoms, and treatments.

1. Degenerative Diseases:
   • These diseases arise from the natural aging process and can result in significant health issues such as heart failure, kidney dysfunction, and skeletal deformities. Aging fish may also develop growths or tumors, leading to reproductive challenges and decreased viability. A common condition within this category is air-bladder disease, which disrupts buoyancy control.
2. Traumatic Diseases:
   • Injuries sustained from fighting or accidental escapes from the aquarium can lead to traumatic diseases. Such injuries may manifest as skin abrasions or internal damage, necessitating careful monitoring and treatment to prevent infections.
3. Congenital Diseases:
   • Congenital diseases result from genetic anomalies present at birth. These may include deformities such as the absence of gill covers or spinal deformities. Such conditions often require careful management and can impact the fish’s ability to thrive.
4. Sudden Shocks:
   • Rapid changes in water chemistry or temperature can induce shock in aquarium fish. Symptoms often include erratic swimming patterns, such as flipping upside down, especially when transitioning between acidic and alkaline water. Fish may also experience stress when moved to water with significantly different temperatures.
5. Infectious Diseases:
   • Infectious diseases are predominantly caused by protozoans and can be transmitted through direct contact or contaminated water. Some notable examples include:
   • White Spot Disease: Caused by Ichthyophthirius sp., this disease presents as white cysts on the skin and fins of affected fish. The infected fish often exhibit signs of irritation, such as rubbing against objects. Treatment involves a ten-day dip in a 5% aqueous solution of Methylene Blue, ensuring the absence of plants, as the chemical can be harmful to them.
   • Velvet Disease: Resulting from Oodinium sp., velvet disease primarily affects labyrinth fishes and some species of carp. Infected fish display gold dust-like spots on their skin, indicative of the parasite. Treatment requires the use of Methylene Blue over ten days and thorough cleaning of the tank environment, including washing gravel and plants.
   • Chilodon Disease: Caused by Chilodon cyprini, this disease affects the skin and gills, leading to asphyxiation. Infected fish may be seen gasping for air at the water surface. Treatment with Methylene Blue or Acriflavin can yield positive results.
   • Costiasis: This condition is induced by the protozoan Costia sp., which targets the fish’s mucus and skin, leading to lethargy and heavy breathing. A 2.5% salt solution dip for fifteen minutes is recommended for treatment.
   • Fin Rot: Bacterial infections entering through damaged fin tissues cause this disease, resulting in tissue degradation. Treatment involves applying a diluted solution of Acriflavin or Penicillin.
   • Columnaris Disease: This bacterial infection, caused by Chondococcus columnaris, typically affects areas near the mouth. Effective treatment includes administering 250 mg of Chloramphenicol per gallon of water.
   • Pop-eye Exophthalmos: Common in Siamese Fighting Fish, this bacterial disease results in swollen, cloudy eyes. If untreated, it can lead to blindness. Treatment involves applying silver eye drops directly to the affected fish.
   • Cotton-Wool Disease: Caused by the fungus Saprolegnia sp., this disease appears as a cotton-like growth at the site of skin damage. Daily treatment with 50% Methylene Blue is necessary to eliminate the infection.
   • Infection by Flukes: Trematodes such as Gyrodactylus and Dactylogyrus cause infections on the body and gills, respectively. Infected fish display pale coloration and damaged fins, and treatment requires a three-day immersion in Methylene Blue.
6. Predatory Threats:
   • In addition to diseases, aquarium fishes are vulnerable to predation from other organisms that may enter the tank. These enemies include Hydra, Piscicola, Great Diving Beetle larvae, and Dragonfly larvae, which can harm fish populations.

Viral Disease in Fish

Viral diseases in fish pose significant challenges to aquaculture and natural fish populations, leading to high mortality rates and economic losses. Understanding the causative agents, symptoms, and potential treatments is crucial for effective management. The following points provide a detailed overview of notable viral diseases affecting fish:

1. Viral Hemorrhagic Septicemia (VHS): This disease is caused by the Viral Hemorrhagic Septicemia Virus (VHSV).
   • Causative Agent: VHSV is a rhabdovirus that can affect multiple fish species.
   • Symptoms: Infected fish often exhibit bulging eyes, bloated abdomens, and a bruised appearance with reddish tints in the eyes, skin, gills, and fins. These symptoms indicate significant internal and external distress.
   • Treatment: Chlorine bleach has been shown to effectively kill the VHS virus, making it a potential disinfectant in aquaculture settings. However, no specific antiviral treatment exists for infected fish, emphasizing the need for prevention.
2. Infectious Hematopoietic Necrosis (IHN): This disease is associated with the Infectious Hematopoietic Necrosis Virus.
   • Causative Agent: The virus is a negative-sense single-stranded RNA virus with a bullet shape.
   • Symptoms: Fish affected by IHN may show abdominal distension, bulging eyes, skin darkening, abnormal behavior, anemia, and fading gills. These clinical signs reflect the severe impact on the fish’s internal systems and overall health.
   • Treatment: Currently, no effective treatment for IHN has been established. Therefore, prevention strategies are critical, including strict isolation, enhanced hygiene practices, and regular testing of fish populations to detect the virus early.
3. Spring Viremia of Carp (SVC): This disease is caused by a specific rhabdovirus affecting carp species.
   • Causative Agent: The virus responsible for SVC is highly contagious among carp populations.
   • Symptoms: Infected fish may exhibit external hemorrhaging, pale gills, and ascites (fluid accumulation in the abdominal cavity), which are indicative of systemic infection and severe distress.
   • Treatment: Currently, efforts are focused on preventing infection through the development of DNA vaccines and immunostimulatory therapeutics. These preventative measures aim to enhance the fish’s immune response to the virus.

Bacterial Disease in Fish

Bacterial diseases in fish are a significant concern in aquaculture, leading to considerable morbidity and mortality. These diseases often arise from environmental stressors, poor water quality, or compromised immune systems. Below is a detailed examination of notable bacterial diseases in fish, encompassing their causative agents, symptoms, and recommended treatments.

1. Columnaris Disease (Cotton Wool Disease): This disease is primarily caused by Flexibacter columnaris.
   • Symptoms: Characteristic grey-white spots appear on the head, fins, gills, and lateral sides of the body. Over time, these spots can ulcerate, forming lesions with reddish peripheries.
   • Treatment: Potassium permanganate (KMnO4) can be used at a concentration of 2-3 ppm in the pond. Fish may also be bathed in a 1-2 ppm KMnO4 solution. For larger fish (greater than 1 kg), an injection of 25 mg streptomycin and 20,000 IU penicillin per kg body weight is recommended. Additionally, Nitrofurazone can be incorporated into the feed at 6.5 g per 100 kg of fish per day.
2. Bacterial Hemorrhagic Septicemia (BHS): Caused by Aeromonas hydrophila, Pseudomonas fluorescens, and A. liquefaciens.
   • Symptoms: This disease is marked by the accumulation of red fluid in the body cavity, destruction of liver cells, green or yellow liver coloration, necrosis of skin, and inflammation of blood vessels. Exophthalmia (bulging eyes) may also be present.
   • Treatment: KMnO4 at 2-3 ppm can be used in the pond, along with Terramycin at a dosage of 65-80 mg per kg body weight for up to 10 days. Larger fish may receive injections of streptomycin (25 mg) and penicillin (20,000 IU) per kg.
3. Edwardsiellosis: Caused by Edwardsiella tarda.
   • Symptoms: This disease leads to scale loss, skin lesions, and damage to muscle tissues. Gaseous wounds develop on the skin, often accompanied by foul odors.
   • Treatment: Tetracycline or sulphonamide can be administered at 8-12 mg per kg of fish through feed. Bath treatments in a 1:20,000 copper sulfate solution for 15 minutes or exposure to a 0.04 ppm iodine solution for 2 hours can also be beneficial. Improving water quality and hygiene, as well as managing stocking density, are crucial for prevention.
4. Vibrio Diseases: Vibrio anguillarum is known to cause multiple conditions, including pike pest.
   • Symptoms: Infected fish display dark skin, bloody exudates, fluid accumulation in the body cavity, and exophthalmia with white spots.
   • Treatment: Proper vaccination is key in preventing these infections. Oxytetracycline, sulphonamide, or Nitrofurazone can be given at a dosage of 8-12 mg per kg of feed, and pond disinfection with slacked lime is also recommended.
5. Furunculosis: Caused by Aeromonas salmonicida.
   • Symptoms: This disease manifests as hemorrhagic septicemia with ulcerative appearances on the skin due to blood capillary rupture.
   • Treatment: Fish should be fed a vitamin-rich diet. Sulfonamide at 5 g per 100 kg of fish per day is advised, along with Chloramphenicol and Oxytetracycline at 5-8 g per 100 kg of fish daily.
6. Fin Rot (Tail Rot): Involves Aeromonas fluorescence and Pseudomonas putrifaciens.
   • Symptoms: Initial signs include slight cloudiness at the outer edges of the fins, progressing to necrosis and potential loss of fins.
   • Treatment: Long baths in acriflavine at 10 g per 100 liters of water or sulfonamide at the same concentration can be used. Dip treatments with emequil at 10 ml per 100 liters for 24-48 hours are also effective. Larger fish may receive Kanamycin injections at 20 mg per kg.
7. Dropsy: Caused by A. hydrophila.
   • Symptoms: Indicators include pale gills, exophthalmia, swelling around the anus, and overall bloating, with affected fish often swimming near the water’s surface.
   • Treatment: Disinfecting the pond with slacked lime (100 kg per hectare) and administering Oxytetracycline or Chloromycin at 5 mg per kg of fish is recommended.
8. Epizootic Ulcerative Syndrome: Caused by a range of pathogens including A. hydrophila, A. salmonicida, and various fungi.
   • Symptoms: Characterized by cauliflower-like deformations of the mouth and numerous red ulcers on the skin.
   • Treatment: Bath treatments with copper sulfate (100-200 g per 100 liters of water) are essential. Additional applications of slacked lime, potassium permanganate, and iodine can be employed to manage this condition.
9. Bacterial Kidney Disease: Caused by Renibacterium salmoninarum.
   • Symptoms: This disease is marked by swollen kidneys, cyst formation, and accumulation of bloody or yellow-brown fluid in the abdominal cavity.
   • Treatment: Erythromycin phosphate can be administered at 1.0 mg per kg body weight, along with bath treatments in a 2 ppm erythromycin solution for up to one hour.

Fungal Diseases in Fish

Fungal diseases in fish represent a significant threat to aquaculture, often arising from environmental stressors, poor water quality, and compromised immune systems. These pathogens can invade various tissues, leading to severe health issues and economic losses in fish populations. Below is a detailed overview of notable fungal diseases affecting fish, their causative agents, symptoms, and treatment strategies.

1. Saprolegniasis and Achlyasis: Caused by Saprolegnia ferox, S. parasitica, and Achlya hoferi.
   • Symptoms: Infected fish exhibit frayed fins, which create an entry point for secondary bacterial infections. The fungi can penetrate muscle tissues, exacerbating the condition.
   • Treatment: A bath treatment using potassium permanganate at a concentration of 100 g per 100 liters of water for 10 minutes is effective. Additionally, a dip treatment with copper sulfate at the same concentration for one minute can help manage the infection.
2. Ichthyosporidiosis: This disease is associated with Ichthyosporidium hoferi.
   • Symptoms: The disease leads to the destruction of the epidermis, resulting in desquamation and the formation of small white necrotic areas due to fungal growth.
   • Treatment: Bath treatments in a 3% salt solution have proven effective. Incorporating copper sulfate into the pond at concentrations of 1-2 ppm can also aid in treatment. For immediate intervention, a bath with formalin at 20 ppm for 2-5 minutes may be applied.
3. Branchiomycosis: Caused by Branchiomysis sanguinis and B. demigrans.
   • Symptoms: This fungal infection leads to necrotic patches on the gills, accompanied by the formation of false membranes made from the proliferation and adhesion of gill epithelium.
   • Treatment: Disinfecting tanks and ponds with quicklime or calcium cyanamide at 2 ppm, following thorough drying of the area, is essential. Fish can also be treated with a 3% salt solution, and the addition of copper sulfate at 1-2 ppm in the pond water is recommended.

Other Parasitic Diseases in Fish

Other parasitic diseases in fish encompass a variety of infections caused by protozoa and metazoan parasites. These pathogens can lead to significant health issues in fish populations, impacting their growth, behavior, and overall survival. Below is a comprehensive overview of various parasitic diseases, their causative agents, symptoms, and recommended treatments.

1. Costiasis: Caused by Costia necatrix.
   • Symptoms: Infected fish present a soft grayish-white film or sheet on their bodies, with severely affected areas exhibiting reddened and hemorrhagic characteristics. Fish may scrape against solid objects in an attempt to relieve irritation.
   • Treatment: Infected fish should be promptly removed from tanks and ponds. It is essential to eliminate leeches, which can serve as vectors for this disease.
2. Whirling Disease: Caused by Myxosoma cerebralis, Ceratomyxa shasta, and various Microsporidium species.
   • Symptoms: The first observable symptom is a rotatory swimming behavior accompanied by black coloration in the caudal region. Affected fish often swim erratically near the water’s surface, displaying the characteristic whirling movement.
   • Treatment: Disinfection of contaminated tanks is critical, using grease-free calcium cyanamide at a rate of 1 kg per square meter. Additionally, applying slaked lime at 80 kg per hectare in ponds prior to stocking fish and utilizing bleaching powder for pre-treatment is recommended.
3. Chilodonellasis: Caused by Chilodonella cyprini.
   • Symptoms: Infected fish show bluish-white opaqueness on their skin, with small pox-like pimples forming around the neck and dorsal fins. Infected fish may exhibit listless swimming and improper respiration as they scrape their bodies against the tank or pond bottom.
   • Treatment: Effective treatments include methylene blue at 3 ppm and acriflavine at 10 ppm. Bathing in copper sulfate at 8 ppm for 15 minutes or using a lysol bath treatment at 200 ppm for 30 seconds are also effective methods.
4. Dactylogyrosis: Caused by Dactylogyrus vastator and D. formosus.
   • Symptoms: This infection results in grayish discoloration of the gill edges. Initially localized to gill filaments, large infestations may spread throughout the fish’s body.
   • Treatment: A short bath in 40% formalin diluted in 100 liters of water for 30 minutes is recommended, as well as bathing in a 3-4% salt solution for 2-3 minutes.
5. Gyrodaclylosis: Caused by Gyrodactylus elegans and G. medius.
   • Symptoms: These parasites primarily attack the skin, resulting in inflamed and reddish areas. Flashing behavior is a common symptom, and in severe cases, the cornea of the eyes may become turbid, leading to blindness.
   • Treatment: A formalin bath treatment at 25 ppm and a NaCl salt solution bath at 2-5% are effective methods for control.
6. Argulosis (Fish Louse): Caused by Argulus foliaceus, A. pellucidus, and A. coregoni.
   • Symptoms: The skin becomes inflamed and reddened due to the parasitic attack, which may also result in secondary bacterial infections, such as hemorrhagic septicemia.
   • Treatment: Effective management includes a short bath in 40% formalin diluted in 100 liters of water for 30 minutes and bathing in a 3-4% salt solution for 2-3 minutes. Additionally, applying cleaner at a rate of 1-1.5 liters per hectare of pond is advisable.
7. Lernaea (Anchorworm): Caused by various species of anchor worms.
   • Symptoms: These parasites commonly attack major carp species and can cause extensive damage in nursery and rearing ponds.
   • Treatment: Similar to argulosis, treatment involves a short bath in 40% formalin for 30 minutes, a 3-4% salt solution bath for 2-3 minutes, and the application of a cleaner at 1-1.5 liters per hectare in ponds.

Precautions and Treatment of Fish Disease

Implementing effective precautions and treatment strategies is vital in managing fish diseases, ensuring the health and sustainability of aquatic ecosystems. A systematic approach can minimize disease incidence and promote optimal fish growth. The following points outline recommended practices for preventing and treating fish diseases:

• Disinfection of Ponds and Tanks: Proper pond management is critical in disease prevention.
  • Bleaching Powder: Apply 50-100 kg of bleaching powder per hectare during pond preparation to disinfect the environment.
  • Quick Lime: For new ponds, use 400-600 kg per hectare; in established ponds, increase to 500-800 kg per hectare to eliminate pathogens.
  • Pre-Stocking Treatments: Treat fish stocks with a 5 ppm formalin solution or a 0.5-2.0% salt solution before introducing them into the pond. For new ponds, apply 5 kg of potassium permanganate (KMnO4) and 5 liters of formalin. For old ponds, use 10 kg of KMnO4, 10 kg of copper sulfate (CuSO4), and 10 liters of formalin.
• Disinfection of Equipment: Instruments used in fish culture should be regularly disinfected to prevent cross-contamination.
  • Formalin and KMnO4 Solutions: Clean equipment with a solution of 5-25 ppm formalin or 250 ppm KMnO4 after thorough washing and sun-drying. Avoid using tools from other ponds to further reduce disease transmission risk.
• Proper Diet: Providing a balanced and nutritious diet is essential for maintaining fish health.
  • Nutritional Composition: Utilize fresh feed with approximately 24% protein, adequate fats, lipids, vitamins, and minerals. Feeding should occur 2-3 times daily, as poor-quality food can lead to stunted growth and increased susceptibility to diseases.
• Grading of Fish: Implement a system for grading fish to reduce competition and stress.
  • Separation by Size and Species: Stock fish of similar size and developmental stages in designated ponds or tanks. Establish separate environments for brooders, fries, fingerlings, yearlings, and juveniles to mitigate mortality rates due to resource competition.
• Eradication of Diseased and Dead Fish: Promptly managing diseased fish is crucial to prevent further outbreaks.
  • Treatment and Removal: Diseased fish can be treated until they regain health; however, dead fish must be removed from the pond immediately and buried away from aquatic environments to prevent contamination.
• Primary Treatment Options: When diseases are detected, initiate primary treatment protocols using various agents.
  • Bath Treatments: Employ potassium permanganate (KMnO4) at concentrations of 100-250 ppm for 2-3 minutes as a bath treatment. A 2-3% salt solution can be used for 1-2 minutes.
  • Regular Applications: KMnO4 should be applied at a rate of 2.5 kg per hectare monthly. Additionally, slaked lime should be administered at 100-200 kg per hectare each month, with netting performed bi-monthly or every 20 days. Implement water exchanges up to 30 cm monthly to maintain water quality.
  • Medication for Severe Infections: In cases of severe disease, antibiotics may be administered. For instance, oxytetracycline can be mixed into fish feed at a rate of 50-60 mg per 100 kg of fish for up to 15 days. Additionally, valuable fish over 1 kg can receive injections of streptomycin (25 mg) and penicillin (20,000 IU).