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

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A couple of years ago, my father raised a pair of juvenile Pleco fish. Everything seemed to be going well until we realized that, at some point, one of them wasn’t growing as expected.

After diving deep into research and experimenting with different solutions, we finally pinpointed the issue. This experience inspired me to write this article.

Why do Pleco fish sometimes experience stunted growth? How can you identify if they’re not growing properly? What size should a Pleco typically reach?

In this article, I’ll shed light on all these concerns, ensuring you leave with all the information you need. Let’s get started.

Is Not Growing in Plecos Normal?

No, it’s not typical for Plecos to stop growing abruptly, especially when they’re young. Healthy Plecos in the right conditions will grow steadily, though the rate can vary.

  • Natural Growth Pattern: Plecos, like the common Plecostomus, can grow up to 12-24 inches in ideal conditions. A noticeable stall in growth suggests something’s off.
  • Age Factor: While Plecos slow down their growth rate as they age, juveniles should exhibit noticeable growth over a span of months.
  • Comparison with Peers: If you’ve had other Plecos or know someone who does, you’ll see a clear difference in growth progression if one isn’t growing as it should.

Signs That Your Pleco Is Not Growing Properly

If your Pleco hasn’t shown any growth in months, it’s a significant sign of an issue. Additionally, behavioral and physical changes can indicate growth problems.

  • Proportional Body: Plecos not growing properly might develop disproportionate bodies – like an elongated body with a small head or vice versa.
  • Loss of Appetite: When Plecos aren’t growing, they might lose interest in food or eat significantly less than their typical hearty appetite.
  • Behavioral Changes: A Pleco that hides excessively, is less active, or shows signs of stress is often not in optimal health.
  • Comparison with Standard Growth Charts: Experienced aquarists often refer to growth charts. If your Pleco is falling behind the typical size for its age, it might not be growing correctly.

Why Is My Pleco Not Growing?

A few reasons might have caused your Pleco to stop growing. Here’s what to consider:

1. Inadequate Diet

One primary reason Plecos might not be growing is that they aren’t getting the proper nutrients. A varied and balanced diet is essential for their optimal growth.

  • Dietary Needs: Plecos require a mix of algae, veggies like zucchini, and high-quality sinking pellets to provide them with a well-rounded diet.
  • Malnutrition Signs: If your Pleco’s colors are faded, and they have a thin body, it’s an indication they might not be getting enough nutrients.
  • Growth Correlation: A Pleco fed with a proper diet will show faster and more steady growth compared to one with inadequate food.

2. Poor Water Quality

Good water quality is paramount for the healthy growth of Plecos. Contaminated or imbalanced water conditions can impede their growth.

  • Toxin Levels: Elevated levels of ammonia, nitrite, and nitrate can be harmful. Plecos in such conditions often become lethargic and stop growing.
  • Importance of pH: Plecos thrive in a pH level of 6.5 to 7.5. Significant deviations can hinder their metabolic processes, affecting growth.
  • Regular Water Testing: It’s crucial to regularly test the water parameters. If your Pleco is not growing, water quality should be one of the first things to check.

3. Overcrowding/Stress

Too many fish in a tank or stressful conditions can stunt the growth of Plecos, making their environment uncomfortable.

  • Space Needs: Plecos, especially the larger species, need ample space to move, forage, and grow. A cramped tank limits their growth potential.
  • Stress Indicators: Frequent hiding, darting movements, or visible injuries from territorial disputes are signs of a stressed Pleco.
  • Tank Recommendations: For a juvenile Pleco, a tank of at least 30 gallons is recommended, with larger tanks required as they grow. Overcrowding can lead to stress and hinder growth.

Also Read: Stress In Pleco Fish

4. Disease or Parasites

The presence of diseases or parasites can significantly impact the health and growth of Plecos. An infected Pleco will use its energy to fight off the illness instead of growing.

  • Common Illnesses: Plecos are sometimes prone to diseases like ich or fungal infections. A Pleco with patchy skin, white spots, or unusual mucus might be sick.
  • Parasitic Invasions: Internal parasites can hinder a Pleco’s ability to absorb nutrients. If your Pleco is eating but still not growing or appears emaciated, parasites might be the culprit.
  • Immediate Action: At the first sign of disease or parasites, it’s essential to diagnose and treat appropriately. A healthy Pleco recovers faster and returns to its natural growth rate.

5. Genetic Factors

Just like in humans, genetics play a role in the growth of Plecos. Some fish may naturally grow slower or smaller due to their genetic makeup.

  • Selective Breeding: Over the years, some Plecos are bred for specific colors or patterns, which might unintentionally select for slower growth rates or smaller sizes.
  • Inherited Traits: If the parent Plecos were of a smaller size or had stunted growth, there’s a chance their offspring might inherit those traits.
  • Acceptance: While you can control diet, water quality, and disease, genetics is something out of our hands. It’s essential to provide the best care but also understand that each Pleco is unique in its growth trajectory.

How to Treat a Pleco That Isn’t Growing

If your Pleco has suddenly stopped growing, simply follow these steps:

1. Providing a Nutrient-Rich Diet

Feeding Plecos a balanced, varied diet is essential for growth. Their diet should match their specific needs to ensure optimal health.

  • High-Quality Pellets: Choose pellets with at least 40% protein content. Brands like Hikari or Fluval are excellent for Plecos.
  • Fresh Vegetables: Feed Plecos thinly sliced zucchini or cucumber 1-2 times a week. Blanching them for 2 minutes softens them just right.
  • Vary the Diet: Introduce treats like bloodworms or brine shrimp once weekly. This boosts their protein intake and encourages growth. I found the Invert Aquatics Mini Algae Discs (link to Amazon) to be excellent as well.
  • Avoid Overfeeding: Feed Plecos once daily, giving what they can consume in 4-5 minutes. Overfeeding can compromise water quality.

Also Read: What Do Plecos Eat?

2. Improving Water Quality

Maintaining pristine water conditions is paramount for Plecos. They thrive best in stable, clean environments that replicate their natural habitat.

  • Regular Water Changes: Perform 25% water changes weekly. This removes toxins and replenishes essential minerals.
  • Test the Water: Use water testing kits to check ammonia, nitrite, and nitrate levels. Ideally, ammonia and nitrite should be at 0 ppm, with nitrates below 20 ppm.
  • Use Good Filtration: Invest in filters rated for tanks larger than yours. For a 50-gallon tank housing a Pleco, a filter rated for 70+ gallons is beneficial.
  • Maintain pH Levels: Keep the pH between 6.5 and 7.5. Using peat moss or driftwood can naturally buffer and stabilize the pH. I personally got the Dr. Moss Malaysian Driftwood (link to Amazon).

3. Reducing Tank Overcrowding

Giving Plecos ample space is vital. A less crowded environment reduces stress and promotes healthier growth.

  • Follow Stocking Guidelines: As a rule of thumb, provide at least 30 gallons for the first Pleco and 20 gallons for each additional one.
  • Monitor Tankmates: Ensure Plecos aren’t bullied by aggressive fish. For example, avoid pairing with fin-nipping species like Tiger Barbs.
  • Provide Hideouts: Include caves or PVC pipes. Plecos need their space to retreat, rest, and feel secure. My recommendation: Jabukosu Aquarium Cave (link to Amazon).
  • Check Tank Size: For larger Pleco species like the Common Pleco, tanks of 100+ gallons may be needed at adulthood. Ensure you have room to upgrade if necessary.

Also Read: Pleco Fish Tank Size

4. Disease or Parasite Treatment

Addressing health issues promptly is essential for a Pleco’s wellbeing. Quick interventions can prevent complications and get your fish back on the growth track.

  • Regular Health Checks: Observe your Pleco daily for changes, such as white spots (indicative of ich) or stringy feces (a potential sign of internal parasites).
  • Medication: Use disease-specific treatments. For instance, for ich, products like API Super Ick Cure (link to Amazon) are effective.
  • Quarantine New Additions: Before adding new fish to the main tank, keep them in a separate quarantine tank for 2-4 weeks to observe for potential diseases.
  • Increase Temperature Gradually: For illnesses like ich, raising the tank’s temperature to 86°F over 24 hours can speed up the life cycle of the parasite, making treatments more effective.

Also Read: Pleco Fish Diseases

5. Considering Genetic Influences

Sometimes, despite providing the best care, a Pleco’s growth might be limited by its genetics. Recognizing this helps set realistic expectations.

  • Research the Breed: Some Pleco species, or specific breeds within a species, may be naturally smaller. For example, the Bristlenose Pleco tends to stay around 4-6 inches.
  • Consult Experienced Breeders: Speak with breeders or hobbyists who’ve raised similar Plecos. They can provide insights into the typical growth patterns of that breed.
  • Observe Parent Fish: If possible, look at the size and growth rate of the parent fish. This can give you a benchmark for what to expect.
  • Acceptance: Recognize that, like humans, every Pleco is unique. Celebrate their individuality and provide the best care, irrespective of their growth rate.

What Are the Ideal Growth Rates for Different Pleco Species?

Growth rates in Plecos can vary widely depending on their species. It’s essential to understand these rates to set proper expectations and ensure their optimal care.

  • Common Plecos (Pterygoplichthys pardalis): These giants, often found in pet stores, can grow 1-2 inches per month in their first year, reaching a total of 12-24 inches in adulthood.
  • Bristlenose Plecos (Ancistrus spp.): These smaller species grow around 0.5-1 inch per month during their early months, capping off between 4-6 inches when fully grown.
  • Zebra Plecos (Hypancistrus zebra): A slow-growing, sought-after species, they grow approximately 0.2-0.5 inches per month, reaching a total length of 3-4 inches.
  • Clown Plecos (Panaqolus maccus): Growing at a rate of about 0.3-0.7 inches monthly, these wood-loving Plecos will typically max out at a size of 3.5-4 inches in adulthood.
  • Royal Plecos (Panaque nigrolineatus): A larger and distinctive species, they grow approximately 0.8-1.5 inches per month during their early stages, reaching 12-17 inches as adults.

Also Read: Why Is My Pleco Not Eating?

Bristlenose Pleco

How Big Should My Pleco Get?

Plecos, belonging to the Loricariidae family, come in a variety of species, each with its unique size when fully mature.

This table provides a handy reference to the typical adult sizes of 25 popular Pleco species:

Pleco SpeciesTypical Adult Size (inches)
Common Pleco (Pterygoplichthys pardalis)12-24
Bristlenose Plecos (Ancistrus spp.)4-6
Zebra Plecos (Hypancistrus zebra)3-4
Clown Plecos (Panaqolus maccus)3.5-4
Royal Plecos (Panaque nigrolineatus)12-17
Gold Nugget Pleco (Baryancistrus xanthellus)8-12
Snowball Pleco (Hypancistrus inspector)5-6
Vampire Pleco (Leporacanthicus heterodon)9-12
Blue Phantom Pleco (Hemiancistrus sp.)6-7
King Tiger Pleco (Hypancistrus debilittera)5-6
Butterfly Pleco (Dekeyseria pulchra)6-7
Sunshine Pleco (Scobinancistrus aureatus)10-12
Flash Pleco (Panaqolus albivermis)4-6
Rubber Lip Pleco (Chaetostoma formosae)4-5
Green Phantom Pleco (Baryancistrus demantoides)6-7
Spotted Raphael Catfish (Agamyxis pectinifrons)5-6
Peppermint Pleco (Parancistrus nudiventris)6-7
Galaxy Pleco (Leporacanthicus galaxias)8-10
Rhino Pleco (Pterygoplichthys scrophus)10-12
Candy Striped Pleco (Peckoltia vittata)4-5
Sultan Pleco (Leporacanthicus joselimai)8-10
Whiptail Catfish (Rineloricaria lanceolata)6-8
Medusa Pleco (Ancistrus ranunculus)4-5
Adonis Pleco (Acanthicus adonis)24-33
Redfin Cactus Pleco (Pseudacanthicus species)12-15

How Can You Measure the Health of a Pleco Beyond Its Size?

While size is a clear indicator of growth, it’s not the only metric to gauge a Pleco’s health. 

There are several other visual and behavioral signs that can shed light on their overall wellbeing.

  • Skin and Fin Health: A healthy Pleco will have smooth skin, free of patches or discolorations. Fins should be fully extended, with no signs of tearing or clamping.
  • Activity Levels: Plecos should be active, especially during the evening and night. Excessive hiding or lethargy can indicate stress or potential health issues.
  • Appetite and Digestion: Regular eating habits and a keen interest in food are good signs. Also, their feces should be consistent in texture, without being too thin or segmented.

What Role Do Tankmates Play in Pleco Growth?

The presence and nature of tankmates can significantly influence the growth and wellbeing of Plecos. Interactions with other fish can either bolster or hinder their development.

  • Stress from Aggression: Aggressive or fin-nipping tankmates, like some Cichlids, can stress Plecos, leading to reduced growth rates and potential injuries.
  • Competition for Resources: In tanks where food or hiding spots are limited, Plecos might face stiff competition, affecting their diet and safety. For instance, larger catfish or other bottom dwellers could outcompete them for food.
  • Beneficial Companions: Peaceful tankmates like Tetras or Rasboras can create a harmonious environment. Their presence can keep water cleaner and provide a stress-free ambiance, promoting better Pleco growth.

Also Read: Why Is My Pleco Turning Black?


For quick readers, here’s a short recap:

  • Healthy Plecos should grow steadily; a halt in growth indicates issues. Juvenile Plecos especially should show growth over several months.
  • A lack of growth can result from inadequate diet, poor water quality, overcrowding/stress, disease/parasites, or genetic factors.
  • Proper care includes a nutrient-rich diet, maintaining ideal water conditions, providing adequate space, addressing health concerns promptly, and acknowledging potential genetic growth limits.
  • Different Pleco species have varied growth rates, such as Common Plecos growing 1-2 inches per month in their first year, while Zebra Plecos grow around 0.2-0.5 inches per month.
  • While size is an evident growth indicator, other health metrics include skin and fin health, activity levels, appetite, and interactions with tankmates.