Why Is My Pleco Not Eating? (5 Practical Solutions)

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A few years ago, my dad looked after two young Pleco fish. Everything went well until one began refusing its food.

After some trial and error, coupled with research, we identified the issue. This motivated me to pen this piece.

Why do Pleco fish stop eating? Is this typical behavior? How can you encourage them to feed again? And how long can they last without nourishment?

I’ll address all these topics in this piece. Let’s get started.

Is Not Eating in Plecos Normal?

Yes, it’s normal for Plecos to occasionally abstain from eating. However, if a Pleco doesn’t eat for more than a week, it’s considered not normal.

  • Habitual Fasters: Plecos are known to occasionally fast, especially when they first enter a new environment or are stressed.
  • Digestion Time: Plecos have a longer digestion time. So, consuming wood and detritus means they might not need daily food.
  • Tank Conditions: If the tank has ample algae and biofilm, Plecos might eat less of the provided food, as they graze on natural sources.
  • Stress Indicators: Like many fish, Plecos might avoid food due to stress. Frequent tank changes, aggressive tankmates, or poor water quality can be culprits.

Why Is My Pleco Not Eating?

Here are the likely factors that may have caused your Pleco fish to stop eating for an extended period of time:

1. Stress or Environmental Changes

Plecos can be sensitive to changes in their environment.

Abrupt modifications or the introduction of aggressive tankmates can lead to increased stress, causing them to avoid food.

  • New Environment: Plecos, when newly introduced to a tank, often take a few days to acclimate and might not eat during this period.
  • Tank Transitions: Moving Plecos between tanks or drastic changes in decor can cause them to become disoriented and reduce their appetite.
  • Aggressive Tankmates: If Plecos feel threatened by aggressive fish, they might hide and abstain from eating to avoid confrontation.

Also Read: Stress In Pleco Fish

2. Poor Water Quality

Plecos thrive in clean water with stable conditions. Drastic changes in pH, high ammonia levels, or nitrite spikes can deter them from feeding.

  • Ammonia and Nitrite: Elevated levels can be toxic to Plecos, leading to reduced appetite and lethargy.
  • Inconsistent pH Levels: Fluctuations in pH can stress Plecos, causing them to lose interest in food.
  • Inadequate Filtration: A poorly functioning filter can lead to a buildup of waste, affecting the water quality and making Plecos reluctant to eat.

3. Illness or Parasites

Like all fish, Plecos are susceptible to diseases and parasitic infestations which can affect their appetite.

  • Visible Symptoms: If Plecos exhibit signs like white spots, clamped fins, or abnormal swimming, they might be sick.
  • Internal Parasites: These can cause Plecos to lose weight even if they eat, or make them avoid food altogether.
  • Lethargy: A sick Pleco might lie at the bottom of the tank, showing minimal interest in its surroundings and food.

4. Unsuitable Diet

Plecos require a balanced and varied diet. Providing them with inadequate or unsuitable food can cause them to lose interest in eating.

  • Specific Dietary Needs: Plecos are primarily herbivores; a diet lacking sufficient vegetables or algae can lead to malnourishment.
  • Low-Quality Food: If the food provided is of poor quality or has lost its nutritional value, Plecos might ignore it.
  • Overfeeding: Plecos can be overfed, leading to leftover food which deteriorates water quality and makes them less interested in fresh food.

5. Aging or Lifespan Issues

Like all living creatures, Plecos undergo changes as they age. As they approach the end of their lifespan, they might naturally eat less.

  • Natural Lifespan: Common Plecos can live up to 10-15 years in well-maintained aquariums. As they near this age, their metabolism might slow down, affecting their appetite.
  • Physical Changes: Older Plecos might show signs of wear, such as faded colors or frayed fins, which can be accompanied by decreased food intake.
  • Less Activity: Senior Plecos might become less active, spending more time resting and showing less interest in feeding.

How to Address a Pleco Not Eating

Here’s what you can do if your Pleco completely stops eating:

1. Stress and Environmental Management

Plecos thrive in stable environments. Identifying and mitigating stressors can boost their eating habits.

  • Safe Hiding Spots: Use driftwood or caves, ensuring spaces of 15 inches for juveniles and up to 30 inches for adult Plecos. I personally picked the Dr. Moss Malaysian Driftwood (link to Amazon).
  • Consistent Environment: Maintain temperatures of 74-80°F and avoid major tank changes; less than 10% of decor alterations monthly is ideal.
  • Gradual Changes: Introduce new elements over 7-10 days, adjusting roughly 5% of tank decor or volume daily.
  • Monitor Tankmates: Aim for 1 Pleco per 20-25 gallons and watch for aggressive species like certain Tetras or Barbs.

Also Read: Pleco Fish Tank Mates

2. Improving Water Quality

Clean water promotes Pleco health. Regular monitoring and maintenance can stimulate appetite.

  • Regular Testing: Employ weekly test kits to check pH (6.5-7.5), ammonia, and nitrite (both ideally at 0 ppm).
  • Water Changes: Implement bi-weekly 25-30% water replacements, always using a reliable dechlorinator beforehand. I found the Tetra AquaSafe (link to Amazon) to be extremely useful.
  • Efficient Filtration: Monthly filter media cleaning is key, and maintain flow rates of 4-5x the tank’s volume hourly.
  • Remove Leftovers: Ensure uneaten food is siphoned out within 24 hours to ward off potential contamination.

3. Addressing Illness or Parasites

Timely care for a sick Pleco can restore health and appetite.

  • Quarantine Practices: New fish should be isolated for 2-3 weeks, preventing potential disease introduction.
  • Observe Symptoms: Regularly check for indicators like white spots, clamped fins, or uncharacteristic swimming behaviors.
  • Medication Use: For suspected ailments, consult aquarist experts and consider treatments like Prazipro or related meds. A good general starting point would be Seachem PolyGuard (link to Amazon).
  • Regular Health Checks: Bi-monthly visual examinations can spot issues early, enabling quicker interventions.

Also Read: Pleco Fish Diseases

4. Offering a Varied and Suitable Diet

Plecos, being diverse in their dietary needs, appreciate a mix of foods. Ensuring they receive a balanced diet can significantly affect their eating behavior.

  • Vegetable Diet: Incorporate zucchini, spinach, and peas, blanching them briefly to soften; these should be staple items in a Pleco’s diet.
  • High-Quality Pellets: Invest in premium sinking pellets or wafers designed specifically for herbivorous bottom-dwellers like Plecos. My recommendation: Invert Aquatics Mini Algae Discs (link to Amazon).
  • Natural Algae Growth: Encourage some controlled algae growth in the tank, as Plecos naturally graze on algae and it aids their digestion.
  • Occasional Protein: Offer treats like bloodworms or brine shrimp once a week, providing essential proteins but not overloading their herbivore-centric system.

Also Read: What Do Plecos Eat?

5. Assessing and Understanding the Natural Lifespan

Every fish has a finite lifespan, and Plecos are no exception. Recognizing and respecting this natural cycle is vital for proper care.

  • Life Expectancy: Common Plecos can live up to 10-15 years in optimal conditions; awareness of their age can set realistic care expectations.
  • Age-Related Changes: Older Plecos may exhibit faded colors, reduced activity, or frayed fins, signaling their advanced age.
  • Appetite Fluctuation: As they age, Plecos may naturally eat less, resembling patterns seen in many senior living organisms.
  • End-of-Life Care: Ensure a peaceful environment, free from stressors, allowing older Plecos a dignified and comfortable latter phase of life.

Are Some Pleco Species More Likely Not to Eat Than Others?

Yes, some Pleco species are indeed more finicky eaters than others. While most Plecos are adaptable, certain species can be particularly selective about their diet.

  • Species Differences: Common Plecos (Hypostomus plecostomus) are often more adaptable to varied diets, while others, like the Zebra Pleco (Hypancistrus zebra), can be more specific in their food preferences.
  • Natural Habitats: Plecos like the Rubbernose or Bulldog Pleco, found in fast-moving streams, might prefer a diet rich in biofilm and algae, making them selective in aquarium settings.
  • Maturity and Diet: Juvenile Plecos are generally more accepting of diverse food types; as they mature, some species develop stronger preferences, making them seem pickier.

Also Read: Why Is My Pleco Not Moving?

Zebra Pleco

What Foods Are Most Appealing to Plecos?

Plecos, by nature, are predominantly herbivores, but they do appreciate variety. Offering a blend of plant-based foods with occasional protein treats is ideal.

  • Vegetable Staples: Leafy greens such as spinach, zucchini slices, and cucumber are favorites among many Plecos, often eagerly devoured when anchored to the tank’s bottom.
  • Algal Sources: Algae wafers or tablets are a hit; they cater to Plecos’ natural inclination to graze on algae, replicating their wild diet.
  • Protein Snacks: While mainly herbivores, Plecos do enjoy the occasional protein boost from bloodworms or brine shrimp, providing essential amino acids and diversifying their diet.

Can Overfeeding or Underfeeding Affect a Pleco’s Eating Habits?

Yes, both overfeeding and underfeeding can significantly impact a Pleco’s eating habits and overall health. Striking the right balance in feeding is crucial for their well-being.

  • Digestive Health: Overfeeding Plecos can lead to bloating and constipation, making them less likely to eat during subsequent feedings.
  • Water Quality: Excess food left uneaten deteriorates, elevating ammonia and nitrate levels in the tank, which can stress Plecos and reduce their appetite.
  • Nutritional Deficiencies: Underfeeding or not providing a varied diet can lead to malnutrition, causing Plecos to become lethargic and show diminished interest in food.

How Does Tank Mate Compatibility Influence a Pleco’s Feeding?

Tank mate compatibility plays a vital role in a Pleco’s comfort and feeding habits. The presence of aggressive or inappropriate tank mates can deter Plecos from eating properly.

  • Competition for Food: Tank mates like Cichlids might outcompete Plecos for food, leaving the Plecos with inadequate nutrition.
  • Aggressive Interactions: Some fish can be territorial and might chase or nip at Plecos during feeding times, making them more hesitant to come out and eat.
  • Hiding vs. Feeding: If constantly threatened, Plecos may prioritize hiding over feeding, especially if they lack ample safe spaces or are outnumbered by aggressive species.

How Often Should You Monitor a Pleco’s Eating Patterns?

It’s essential to observe your Pleco’s eating habits regularly, ideally during every feeding session.

Consistent monitoring can help you detect any changes early, ensuring your Pleco remains healthy.

  • Daily Observations: While Plecos may not eat every day, watching their interaction with food items daily can offer insights into their appetite and preferences.
  • Weekly Notes: Keeping a weekly log of what and how much they eat can help identify patterns or changes over time, offering a broader perspective.
  • Post Environmental Changes: After any significant changes in the tank – like introducing new fish or adjusting decor – monitor Plecos closely for a week to assess their feeding response.
  • Regular Weight Checks: Monthly weighing or visual examinations can indicate whether Plecos are getting adequate nutrition, even if daily food intake seems normal.

Also Read: Why Is My Pleco Not Growing?

How Long Can Plecos Go Without Food?

Plecos can survive without food for a relatively extended period due to their slow metabolism and ability to source nutrients from their environment.

In ideal conditions, a healthy Pleco can go without food for up to 7-10 days, although it’s not recommended.


For quick readers, here’s a short recap:

  • Plecos might occasionally fast, especially when newly introduced to a tank or stressed, but abstaining for over a week is concerning.
  • Factors causing Plecos to stop eating include stress, poor water quality, illness, an unsuitable diet, or aging/lifespan issues.
  • Addressing a non-eating Pleco involves managing stress, maintaining water quality, treating illnesses, offering a balanced diet, and understanding the natural lifespan.
  • Some Pleco species are pickier eaters, with diet preferences varying based on species and natural habitats.
  • Monitoring a Pleco’s eating patterns regularly, especially during changes in the tank environment, is crucial to ensure their health.