Pleco White Fungus Disease: Causes, Treatment, Prevention

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It is pretty common to wake up one day and find one of your fish covered with a white, cotton-like patch on its body. That happened to my Pleco a few months ago.

Obviously, it was a white fungus disease, which automatically raises some questions.

Why do some Plecos get infected? What are the typical symptoms? How do you treat them, and what is the prognosis? Can you prevent this from happening again?

In this article, I’ll discuss all these questions and many more so you leave with all the information you need. Let’s get started.

What Is Fungus in Plecos?

Fungus in Plecos refers to fungal infections that can affect the Plecostomus fish, often presenting as white, cottony growths on their body or fins.

These infections can compromise the health of Plecos and require timely intervention.

  • Visible Symptoms: Plecos with fungal infections show white, fluffy patches on their body. This cotton-like growth can hinder their movement.
  • Causes: Outbreaks arise from factors like poor water quality or injuries. Decaying food in the tank can also be a culprit.
  • Treatment Options: Antifungal medications and optimal water conditions are key. Proper tank hygiene aids in Pleco recovery.
  • Prevention: Monitoring water and providing a balanced diet helps. Regular tank maintenance and injury care are vital.

Also Read: Pleco Fish Diseases

How Does a Fungal Infection Develop in Plecos?

A fungal infection in Plecos unfolds as fungal spores latch onto the fish and find suitable conditions to multiply.

Over time, this results in visible fungal growth, usually resembling white, cotton-like patches on the Plecos.

  • Initial Attachment: In the beginning, fungal spores adhere to the Plecos’ skin, especially in areas like wounds or weakened tissues, initiating the infectious process.
  • Germination Stage: Under optimal conditions, these spores germinate, growing thread-like structures called hyphae that dig into the Pleco’s tissues.
  • Colonization: As the fungus establishes itself, it forms a mycelium — a dense network of hyphae, which covers the affected area and starts consuming the Pleco’s organic matter.
  • Visible Growth: With the progression of the infection, the mycelium produces spore-filled structures. This results in the noticeable white, fluffy patches commonly associated with fungal infections in Plecos.

Symptoms of Fungus Disease in Plecos

Symptoms of fungus disease in Plecos are noticeable changes that indicate the presence of fungal infections in these fish.

Recognizing these signs early is essential for the health and well-being of Plecos.

  • White Patches: Plecos affected will have white, cotton-like growths. These are often the most noticeable signs of fungus.
  • Clamped Fins: Infected Plecos might keep their fins close to the body. This indicates discomfort and potential fungal invasion.
  • Scratching Behavior: Plecos may rub against tank decorations or gravel. It’s an attempt to relieve irritation caused by fungus.
  • Lethargy: Plecos with fungal infections often become less active. You’ll notice them moving slower or staying in one place.
  • Loss of Appetite: An infected Pleco may eat less or even refuse food. Weight loss can become evident over time.
  • Breathing Difficulties: Plecos may exhibit rapid gill movements. It’s a sign they’re struggling to breathe due to gill fungus.
  • Frayed or Rotting Fins: Fungal infections can cause fin deterioration. Watch for edges that look torn or eroding in Plecos.

Also Read: Pleco Fish Fin Rot

What Causes Fungus Disease in Plecos?

Several factors may cause a fungal infection to develop. Here are the main ones:

1. Bad Water Conditions

Unfavorable water conditions enhance the probability of fungal infections in Plecos. When these parameters are off, Plecos’ health is directly threatened.

  • Ammonia and Nitrites: Elevated levels of these toxins in the tank can be quite detrimental. Ideally, both should always measure 0 ppm for the absolute health and safety of Plecos.
  • Improper pH Levels: Plecos function best within a pH spectrum of 6.5 to 7.5. Any substantial deviation from this can heighten stress and pave the way for fungal issues.
  • Inconsistent Temperatures: Plecos favor consistent temperatures between 72-86°F (22-30°C). Any unexpected temperature spikes or drops can make them more susceptible to diseases.

2. Injuries

Even the slightest physical trauma can serve as a gateway for fungal spores, escalating the risk of infection.

  • Sharp Decor: Tank decorations with jagged or sharp contours can inadvertently injure Plecos, exposing them to potential infections.
  • Aggressive Tank Mates: Certain aggressive fish species have tendencies to nip and harass Plecos. Such behavior often results in injuries that are open to infections.
  • Improper Handling: Moving or attempting to net Plecos without utmost care can lead to unintentional wounds, increasing fungal risks.

3. Stress

Elevated stress levels in Plecos weaken their immune defenses, rendering them more vulnerable to fungal invasions.

  • Overcrowded Tanks: Tanks filled beyond capacity can exert immense stress on Plecos. Such environments can seriously compromise their immune defenses.
  • Loud Noises: Plecos have a heightened sensitivity to abrupt, loud sounds, which can significantly elevate their stress and diminish immunity.
  • Rapid Environmental Changes: Sudden alterations in the tank environment, like drastic light changes or water parameter shifts, can induce stress. 

4. Too Much Food

Overfeeding leads to conditions that indirectly propagate fungal issues in the tank.

  • Decomposing Leftovers: Excess unconsumed food decays and compromises water quality. This decay fosters fungal growth, posing a direct threat to Plecos.
  • Nutrient Imbalance: Overfeeding can alter the nutrient balance of the tank. Such imbalances might boost fungal populations, jeopardizing Plecos’ health.
  • Increased Waste Production: Overfed Plecos produce more waste. Increased waste can lead to spikes in ammonia and nitrites, factors known to stress and weaken Plecos.

5. Adding Sick Fish or Contaminated Items

Introducing ailing fish or tainted equipment can directly trigger fungal outbreaks.

  • Unchecked Quarantine: New fish, if not quarantined adequately, can introduce pathogens. These newcomers can carry and spread fungal spores to Plecos.
  • Contaminated Equipment: Using tools or adding decorations from infected environments can harbor spores. These contaminants, when introduced, elevate fungal risks for Plecos.
  • Shared Water Sources: Water from an infected tank or source, when added, can introduce harmful fungal agents. Plecos exposed to such water become prime targets for infections.

How Can You Treat Plecos with Fungus?

If you believe that your Pleco has caught a fungal infection, simply follow these steps:

1. Use Anti-Fungal Solutions

Utilizing specific anti-fungal treatments helps to directly combat the fungus affecting Plecos. These solutions are vital for effective treatment.

  • Medicated Baths: Submerge infected Plecos in a 5 mg/L Methylene Blue solution for 20 minutes. Ensure the water is aerated and monitor the Plecos for signs of distress.
  • Direct Application: Using a soft cotton swab, gently apply a solution of diluted Povidone-iodine (2% concentration) on localized fungal growths, ensuring minimal stress to the Plecos.
  • Tank Treatment: Introduce anti-fungal agents like Fluconazole at 5 mg per gallon or Malachite Green at 0.05 mg/L. Carefully observe Plecos for any adverse reactions during treatment.
  • Quarantine Treatment: Isolate affected Plecos in a separate 10-gallon tank, maintaining a temperature of 78°F. Administer recommended anti-fungal dosages and monitor daily.

2. Make Water Better

Improving water conditions is paramount to aiding Plecos’ recovery and preventing future outbreaks.

  • Regular Testing: Use testing kits to maintain ammonia and nitrite levels at 0 ppm. Ensure the pH stays within 6.5 to 7.5 for optimal Plecos health. I personally use the API FRESHWATER MASTER TEST (link to Amazon) for accurate measures.
  • Frequent Water Changes: Replace 20-30% of the tank water weekly. Always use dechlorinated water that matches the tank’s temperature.
  • Effective Filtration: Employ a robust filter capable of handling your tank’s volume. Clean the filter media every month without using chlorinated water. My recommendation: Fluval C4 Power Filter (link to Amazon).
  • Limit Organic Waste: Vacuum the substrate regularly, aiming for once a week, to reduce decaying matter that can harbor fungal spores.

3. Care for Injuries

Prompt attention to any injuries can prevent them from becoming gateways for fungal infections.

  • Salt Treatment: Add API AQUARIUM SALT (link to Amazon) at 1 teaspoon per gallon to the tank. This mild solution aids in healing wounds on Plecos.
  • Observation: Check Plecos daily for cuts, nicks, or scrapes. Early detection can enable quicker interventions, reducing complications.
  • Safe Environment: Ensure the tank decor is devoid of sharp edges. Consider smooth rocks and driftwood that won’t injure Plecos.
  • Gentle Handling: When transferring or netting Plecos, be delicate. Using a soft mesh or container can reduce potential injuries.

4. Limit Stress

Reducing stress is key to bolstering Plecos’ immunity and overall well-being.

  • Stable Environment: Maintain a consistent temperature between 72-86°F and avoid sudden changes in lighting or water parameters.
  • Provide Hideouts: Introduce caves or hiding spots in the tank. These refuges offer Plecos a sense of security and comfort. My Plecos absolutely love this Jabukosu Aquarium Cave (link to Amazon).
  • Manage Tank Population: Avoid overcrowding by ensuring adequate space per Pleco. A 40-gallon tank is spacious enough for an adult Pleco.
  • Dim Lighting: Plecos enjoy low light settings. Dim down bright lights and think about using soft LED lighting for their ease.

5. Monitor Food Portions

Controlling food quantities helps avoid too much organic waste, which might lead to fungal conditions harmful to Plecos.

  • Portion Control: Feed Plecos an amount they can consume within 2-3 hours. Overfeeding leads to waste, which can compromise water quality.
  • Quality Over Quantity: Offer high-quality pellets or wafers that are less likely to disintegrate quickly. This ensures Plecos get their nutrients without polluting the water. I use these Invert Aquatics Mini Algae Discs (link to Amazon).
  • Scheduled Feedings: Stick to a consistent feeding schedule, ideally once or twice a day. This consistency helps Plecos establish a routine, reducing overeating tendencies.
  • Observe Consumption: Watch Plecos during feedings. If they leave behind uneaten food, reduce the portion in the subsequent feeding.

6. Isolate New or Sick Fish

Establishing a quarantine or hospital area is essential. It provides a space to observe new additions or treat unwell Plecos without risking the health of the entire community.

  • Appropriate Tank Size: Set up at least a 10-gallon quarantine tank. This ensures ample space for Plecos to move, aiding in stress reduction during their isolation.
  • Consistent Water Conditions: Mimic the main tank’s water parameters in the quarantine tank. This continuity reduces stress for Plecos and aids in their recovery or acclimatization process.
  • Regular Observation: Check quarantined Plecos daily for any signs of disease or stress. Early detection allows for timely intervention, increasing recovery chances.
  • Equipment Sterilization: After use, sterilize equipment like nets or siphons that come into contact with the quarantine tank.

Should I Isolate Plecos with Fungus Disease?

Yes, isolating Plecos with fungus disease is highly recommended. It prevents the spread of the infection to other fish and provides a controlled environment for treatment.

  • Disease Containment: By isolating infected Plecos, you limit the risk of the fungal spores spreading, thus protecting your other fish from potential infections.
  • Focused Treatment: In a quarantine tank, you can precisely dose medications and treatments, ensuring the infected Plecos receive targeted care without affecting tankmates.
  • Monitoring Ease: With fewer fish in a quarantine setup, it’s simpler to observe the Plecos’ condition, track their recovery, and spot any complications early on.

How Do Plecos with Fungus Disease Usually Heal?

When diagnosed early and given the appropriate care, Plecos with fungus disease often make a complete recovery. However, the time and prognosis depend on several factors.

  • Early Diagnosis: Plecos diagnosed in the initial stages of the fungal infection typically heal faster, often within 7-10 days, when treated promptly.
  • Severity Matters: Mild infections might take a week to heal, while severe cases, with extensive fungal growth, can take upwards of 2-3 weeks with consistent treatment.
  • Medication Response: Not all fungal strains respond to the same treatments. Sometimes, trial and error are needed, which can extend the healing time for some Plecos.
  • Supportive Care: Along with anti-fungal treatments, maintaining optimal water quality and reducing stress are critical. Plecos in such environments often heal more efficiently and are less likely to face recurrence.

How Do I Keep My Tank Fungus-Free?

After treating a Pleco with a fungal infection, it’s vital to ensure the tank doesn’t have any lingering fungal spores to prevent reinfection.

Here’s your guide to ensure a safe environment for your Plecos and other tankmates:

  • Deep Cleaning: Go for a thorough clean, draining 50% of the tank’s water and refilling it with fresh, dechlorinated water to minimize any leftover fungal spores.
  • Sanitize Decorations: Take out and sanitize all decorations, rocks, and plants. For example, a 10-minute soak in a 1:10 bleach solution can get rid of fungal traces.
  • Filter Upkeep: Cleanse and change the filter media. If you can, add a UV sterilizer to your filtration setup to combat fungal spores, making the space safer for Plecos.
  • Medication Touch-Up: Think about introducing a comprehensive antifungal treatment to the tank, adhering to the recommended dose, to clear out any remaining harmful fungal spores.
Fungus on pleco eggs

How to Prevent Fungus Disease in the Future?

To ward off fungal diseases, it’s all about proactive care and upholding a wholesome tank ambiance. Consistent checks and care can shield your Plecos from future fungal problems.

  • Diet Matters: Offer Plecos top-notch food; subpar or expired food can bring fungi into the environment.
  • Mind the Crowd: Don’t let the tank get too populated. For example, sticking to one Pleco for every 20 gallons can help cut down on stress and health hazards.
  • Consistent Health Lookouts: Regularly inspect your Plecos for any unusual signs, ensuring you catch any problems early.
  • Steer Clear of Stressors: Avoid sudden temperature swings, hostile tankmates, or bad water conditions, as these can stress Plecos and heighten their susceptibility to fungi.
  • Adopt Protective Steps: Occasionally add aquarium salt or antifungal solutions, following the product’s instructions, to make the surroundings inhospitable to fungal growth.

Also Read: Pleco Fish Hole In The Head


For those of you in a rush, here’s a brief summary:

  • Fungal infections in Plecos, characterized by white, cottony growths, are a common health issue that can hinder their movement and require timely treatment.
  • Fungal infections develop as fungal spores attach to Plecos’ skin, germinate, colonize, and result in visible white, fluffy patches.
  • Recognizable symptoms of fungal disease in Plecos include white patches, clamped fins, scratching behavior, lethargy, loss of appetite, breathing difficulties, and fin deterioration.
  • Various factors like poor water conditions, injuries, stress, overfeeding, and introducing sick fish or contaminated items can lead to fungal infections in Plecos.
  • To help Plecos with fungus, use anti-fungal solutions, improve water quality, care for injuries, reduce stress, regulate food amounts, and set up a separate area for new or sick fish.