Why Does My Pleco Have a Sunken Stomach?

Home/Store/Fish and Aquaria Related Articles/Why Does My Pleco Have a Sunken Stomach?

🐟 Why Does My Pleco Have a Sunken Stomach?


1️⃣ Starvation / Malnutrition 🍽️

  • ❌ Not enough food – Plecos cannot survive on poop or scraps.
  • 🟢 What they need instead:
    • 🍃 Algae wafers (staple diet)
    • 🥒 Vegetables – zucchini, cucumber, spinach, peas (blanched)
    • 🪵 Driftwood – essential for digestion in many species
    • 🍤 Protein treats – shrimp pellets, bloodworms (occasionally, depending on species)
  • 🔎 Signs of malnutrition:
    • Belly looks hollow, wrinkled, or pinched in
    • Pleco becomes less active and hides more
    • Fins may look clamped

2️⃣ Internal Parasites 🪱

  • 🐟 Wild-caught plecos are more likely to carry them.
  • 🔎 Symptoms:
    • Sunken belly even if pleco is eating regularly
    • 💩 White, stringy poop
    • 😴 Lethargy – pleco hides constantly, avoids food
  • 🛠️ Solution:
    • Medicated foods with praziquantel, levamisole, or metronidazole (depends on parasite type)
    • Keep water extra clean during treatment

3️⃣ Stress or Poor Water Quality 🌊

  • 💨 Low oxygen, 🌡️ wrong temperature, or 💀 high ammonia/nitrite can cause stress.
  • 🔎 Signs:
    • Gasping at surface
    • Not eating
    • Belly looks thin because pleco won’t forage
  • ✅ Fix:
    • Strong filtration + good aeration (air pump + sponge filter)
    • 🧪 Test water weekly (Ammonia: 0, Nitrite: 0, Nitrate < 40ppm)
    • 🌊 Regular gravel vacuuming + water changes

4️⃣ Optical Illusion (Normal Behavior) 👀

  • 🪞 Sometimes when a pleco is stuck to the glass/acrylic, its stomach looks sunken in.
  • 🌀 This happens because the suction pressure of its mouth pulls its body tight against the surface.
  • ✅ If the belly looks round and normal when on the bottom, driftwood, or decorations, this is not a health issue.

✅ What To Do If Your Pleco’s Belly Looks Sunken

  • 🍃 Feed algae wafers daily (nighttime is best since plecos are nocturnal).
  • 🥒 Supplement with blanched veggies 2–3x a week.
  • 🪵 Always keep driftwood in the tank (especially for bristlenose, common, royal plecos).
  • 💧 Maintain clean water & strong oxygen levels.
  • 🧪 If belly stays hollow → treat for parasites.

👉 Bottom Line:

  • If your pleco only looks “sunken” when on the glass → 🟢 Normal illusion.
  • If your pleco always looks sunken, hides, or is weak → ⚠️ Underfed, stressed, or sick.

🐟 Pleco Belly Check – Healthy vs. Sunken

✅ Healthy Belly ⚠️ Sunken Belly
🔎 Appearance Rounded, smooth, slightly full Hollow, pinched-in, wrinkled look
🪞 On Glass May look slightly pressed due to suction (normal illusion) Still looks hollow even when off the glass
🍽️ Feeding Actively forages at night, eats algae wafers & veggies Ignores food, or eats but still gets thinner
💩 Poop Brown/green, solid strands = normal digestion White, stringy poop = possible parasites
⚡ Energy Active at night, explores tank, attaches to surfaces Lethargic, hides constantly, low movement
🌊 Water Quality Response Thrives in clean, oxygen-rich water Becomes weaker if ammonia/nitrite are present
🧩 Cause Well-fed with balanced diet + driftwood Starvation, parasites, stress, poor water quality

✅ What To Do

  • 🍃 Feed algae wafers daily
  • 🥒 Add blanched veggies 2–3x weekly
  • 🪵 Provide driftwood for rasping & digestion
  • 💧 Keep water parameters stable
  • 🧪 If belly remains sunken → treat for internal parasites

👉 Quick Tip: If your pleco looks thin only when stuck on the glass → 🟢 that’s just suction pressure. If it looks thin all the time → ⚠️ that’s a real problem.


  • Search for Fish
  • My Account
  • Track Orders
  • Favorite Fish.
  • Fish Shopping Bag
Powered by Lightspeed
Display prices in:USD
Skip to main content
ENES
Menu
Home
Shop For Fish
Terms & Conditions/FAQ
Shipping & Payments
About Us
Contact Us
© Jasons Plecos & Cichlids LLC 2017-2025
Language:
ENES
Terms & ConditionsPrivacy PolicyShipping & Payment InfoReturn PolicyQuarantine Your FishReport abuse
Powered by Lightspeed