Why Is My Pleco Swimming Erratically? (5 Easy Solutions)

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Plecos are hardy fish, which is why they’re a favorite among many fish enthusiasts. Their captivating beauty and intriguing behavior are truly undeniable.

That said, they aren’t without their challenges. A while back, I observed one of my Plecos swimming erratically, displaying signs of discomfort that truly worried me.

Thankfully, with diligent research, I found a solution to the issue. Now, I’m here to walk you through the exact steps to address similar concerns. Let’s dive in.

Is Erratic Swimming in Plecos Normal?

No, erratic swimming in Plecos is not normal. It can be an indication of underlying issues that need to be addressed.

  • Stable Nature: Plecos are generally bottom-dwelling fish, preferring to cling to surfaces and stay relatively still. Erratic movement contrasts their natural behavior.
  • Size Consideration: Mature Plecos can grow up to 24 inches long in the wild, making erratic swimming dangerous in confined spaces like aquariums.
  • Energy Expenditure: Plecos have a low metabolic rate and don’t waste energy. Uncharacteristic swimming patterns can deplete their energy reserves.
  • Stress Indication: In the wild, Plecos would only swim erratically if they were under threat. Such behavior in an aquarium can indicate stress or discomfort.

Why Is My Pleco Swimming Erratically?

A few reasons might have caused your Pleco to swim this way. Here’s what you should know:

1. Poor Water Quality

Plecos, like all aquarium fish, require a certain level of water quality to remain healthy.

If the water parameters drift from the ideal, your Pleco might start displaying erratic behaviors as a reaction.

  • Ammonia Levels: Elevated ammonia in the tank can cause gill damage in Plecos, making them gasp for air and swim erratically.
  • Incorrect pH: Plecos thrive in slightly acidic to neutral pH levels (6.5-7.5). A drastic change can lead to discomfort and abnormal swimming.
  • Toxin Accumulation: Over time, uneaten food and waste can decompose, releasing toxins. Plecos exposed to these toxins may display irregular behaviors.

2. Diseases or Parasites

Infections and infestations can alter a Pleco’s usual behavior. If your Pleco is swimming erratically, it might be suffering from some health issues caused by diseases or parasites.

  • Ich Infection: Commonly known as “white spot disease,” Ich can make Plecos scratch against objects and show erratic movement.
  • Internal Parasites: Parasites affecting the internal organs can lead to bloating and unusual swimming patterns in Plecos.
  • External Flukes: These tiny parasites attach to a Pleco’s body, causing discomfort and leading to abnormal swimming as the fish tries to dislodge them.

3. Stress or Fear

Just like any other animal, Plecos can experience stress or fear. Certain tank conditions or stimuli can make them anxious, leading to erratic swimming.

  • Tankmates: Aggressive or overly active tankmates can intimidate Plecos, causing them to swim away rapidly.
  • Insufficient Hiding Places: Plecos are nocturnal and love hiding. A tank without enough caves or hiding spots can make them feel exposed and stressed.
  • Sudden Changes: Drastic alterations in light, noise, or even the movement around the tank can startle Plecos, leading to a sudden change in their swimming pattern.

Also Read: Stress In Pleco Fish

4. Unsuitable Tank Mates

Compatibility is a key factor in aquarium setups. When Plecos are housed with unsuitable tank mates, it can trigger irregular behaviors, including erratic swimming.

  • Predatory Fish: Housing Plecos with predatory species can make them constant targets, leading to stressed and abnormal movements as they attempt to escape.
  • Territorial Disputes: Some fish can become territorial, especially during breeding. Plecos caught in these disputes may dart around trying to avoid confrontations.
  • Overcrowding: Too many fish in a confined space can increase competition for resources. Plecos, feeling trapped or in competition, might swim erratically as a result.

5. Inadequate Diet or Nutrition

Plecos have specific dietary needs. If these needs aren’t met, it can lead to malnutrition, affecting their overall health and behavior.

  • Lack of Variety: Plecos need a varied diet, including algae, veggies, and specific commercial foods. A monotonous diet can lead to nutrient deficiencies and unusual behaviors.
  • Malnutrition Symptoms: A Pleco not receiving adequate nutrition might exhibit signs like sunken eyes or a thin body, along with erratic swimming as they search for food.
  • Digestive Issues: Foods not suitable for Plecos can cause digestive troubles. When feeling unwell, Plecos might dart or swim oddly as a sign of discomfort.

How to Treat Plecos That Swim Erratically

To help a Pleco that is darting around, simply follow these steps:

1. Improving Water Quality

Ensuring pristine water conditions is paramount for the health of Plecos. Any inconsistency can trigger abnormal behaviors like erratic swimming.

  • Regular Testing: Using kits, test water weekly for ammonia, nitrite, and pH; ideal pH for Plecos is between 6.5 and 7.5.
  • Water Changes: Implement 25% water changes weekly, ensuring temperature consistency to avoid shocking Plecos.
  • Filter Maintenance: Clean or replace filter media monthly; a clogged filter compromises water clarity and oxygen levels for Plecos.
  • Use Conditioners: Add water conditioners during changes to neutralize chlorine and heavy metals, which are harmful to Plecos. I do that with the Tetra AquaSafe (link to Amazon).

2. Diagnosing and Treating Diseases or Parasites

The presence of diseases or parasites can greatly distress Plecos. Early diagnosis and treatment are essential to their recovery.

  • Quarantine New Fish: Before introducing them to the main tank, keep newcomers in a separate tank for 2 weeks to observe for illnesses.
  • Medication: Consult experts or pet stores for appropriate treatments. For Ich, for example, medications like Coppersafe (link to Amazon) are effective.
  • Salt Baths: For external parasites, a mild salt bath can provide relief; use 1-2 teaspoons of aquarium salt per gallon for short durations.
  • Regular Observations: Monitor Plecos daily for symptoms like white spots, lethargy, or scratching against objects, indicating potential health issues.

Also Read: Pleco Fish Diseases

3. Providing a Safe and Stress-Free Environment

Plecos thrive in environments that mimic their natural habitats. Such surroundings reduce stress and encourage natural behaviors.

  • Provide Hiding Places: Introduce caves, driftwood, or plants. Plecos, being nocturnal, appreciate shaded spots to rest during daylight hours. My Plecos love this Jabukosu Aquarium Cave (link to Amazon).
  • Tank Size Matters: Ensure spacious accommodations; for a common Pleco, a minimum of 55 gallons is recommended to allow natural movement.
  • Minimize External Stress: Place the aquarium in a low-traffic area and avoid sudden lighting changes to prevent startling Plecos.
  • Choose Tankmates Wisely: Introduce peaceful species; avoid aggressive or overly active fish that might disturb or threaten Plecos.

Also Read: Do Plecos Need Hiding Spots?

4. Reviewing and Adjusting Tank Companions

Choosing the right tankmates for Plecos is critical. Unsuitable companions can induce stress and erratic behavior in these bottom dwellers.

  • Research Compatibility: Before adding new fish, ensure they coexist harmoniously with Plecos; some cichlids, for instance, might be too aggressive.
  • Monitor Interactions: Regularly observe tank dynamics; bullying or territorial disputes can be detrimental to Plecos’ well-being.
  • Separation Tanks: If aggressive behaviors persist, consider setting up a separate tank or partition for aggressive fish to safeguard Plecos.
  • Population Control: Overcrowding adds stress. Maintain a ratio of roughly one Pleco per 30-40 gallons to provide ample space and resources.

Also Read: Pleco Fish Tank Mates

5. Ensuring a Balanced Diet

Diet plays a fundamental role in Plecos’ health. A nutritionally rich and varied diet can prevent many health concerns, ensuring their optimal well-being.

  • Diverse Foods: Rotate between algae wafers, blanched veggies (like zucchini), and specific Pleco pellets to meet their nutritional needs.
  • Avoid Overfeeding: Give food amounts they can consume in 2-3 hours to prevent leftover decay, which can harm water quality.
  • Observe Eating Habits: Monitor Plecos during feeding; a sudden lack of appetite can be an early sign of underlying issues.
  • Supplemental Nutrition: Occasionally introduce vitamin-enriched foods or treats, ensuring Plecos receive all essential nutrients for a robust immune system. My recommendation: Seachem Nourish (link to Amazon).

Also Read: What Do Plecos Eat?

Are Some Pleco Species More Prone to Erratic Swimming Than Others?

Yes, certain Pleco species can be more inclined towards erratic swimming than others, largely due to their individual habits and natural environments.

However, it’s essential to remember that most Plecos are naturally calm, so any erratic behavior can signal an issue.

  • Common Plecos: Being more adaptable, they’re usually steadier in behavior. However, in smaller tanks (less than 55 gallons), even they can show distress.
  • Zebra Plecos: Originating from fast-flowing rivers, they’re more active swimmers, which might be misconstrued as erratic in confined spaces.
  • Rubber Lip Plecos: These are relatively peaceful, but they’re sensitive to water parameter changes, leading to sudden bursts of abnormal movement.
  • Bristlenose Plecos: Renowned for their calm demeanor, if they exhibit erratic swimming, it’s almost always a sign of distress or environmental issues.
  • Royal Plecos: They prefer wood in their diet and environment. Without it, they can become restless, potentially leading to erratic swimming patterns.

Also Read: Why Is My Pleco Fish Shaking?

How to Prevent Plecos from Swimming Erratically in the Future?

Ensuring a stable, stress-free environment tailored to the needs of your Pleco species is crucial.

By being proactive and understanding their requirements, you can prevent most erratic swimming behaviors.

  • Tank Size Consideration: Provide ample space; for instance, common Plecos need at least 55 gallons to thrive and exhibit natural behaviors.
  • Stable Water Parameters: Maintain water parameters consistently; abrupt pH changes or ammonia spikes can distress Plecos, leading to abnormal swimming.
  • Natural Environment Simulation: Create a habitat mirroring their natural surroundings, like fast currents for Zebra Plecos, ensuring comfort.
  • Regular Health Checks: Periodic checks for parasites and diseases can preclude health-related erratic behaviors. Quarantine new additions to prevent disease spread.
  • Tailored Diet: Understand and cater to the dietary needs of your Pleco species. For Royal Plecos, a wood-rich environment and diet can maintain their calm disposition.

Also Read: Why Is My Pleco’s Mouth Wide Open?


For quick readers, here’s a short recap:

  • Erratic swimming in Plecos indicates potential health or environmental issues, contrasting their natural behavior.
  • Factors causing erratic swimming include poor water quality, diseases/parasites, stress/fear, unsuitable tank mates, and inadequate nutrition.
  • Treating erratic swimming involves improving water quality, treating diseases, providing a stress-free environment, adjusting tank companions, and ensuring a balanced diet.
  • Different Pleco species, like Zebra or Royal Plecos, have unique behaviors and environmental preferences that influence their swimming patterns.
  • Preventing erratic swimming involves offering ample tank space, maintaining stable water parameters, simulating their natural environment, conducting regular health checks, and providing a species-specific diet.