What to Do if Your Aquarium Fish Are Sick?

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🐟🩺 What to Do if Your Aquarium Fish Are Sick


🔎 Step 1: Identify Symptoms

🐟 Physical Symptoms

  • ⚪ White spots → Ich (Ick) — or possibly Epistylis (commonly confused!)
  • 🩸 Red streaks or sores → Bacterial infection
  • 🦠 Cotton-like patches → Fungal infection OR Columnaris (bacterial “cotton wool”)
  • ✂️ Frayed fins → Fin rot
  • 🎈 Bloating → Swim bladder disorder, constipation, parasites
  • 🪱 Visible worms/eggs → Parasites
  • 🫁 Gasping → Ammonia burn, gill flukes, low oxygen

😟 Behavioral Symptoms

  • 💤 Lethargy
  • 🌀 Erratic swimming
  • 🧽 Flashing (scratching on surfaces)
  • 🍽️ Loss of appetite
  • 🫀 Rapid gill movement

⚠️ Important Note on Diagnosis

Some fish illnesses look almost identical:

  • ❄️ Ich vs. Epistylis → Both look like white spots, but ich responds to heat + ich meds, while Epistylis needs antibacterial treatment.
  • 🍄 Fungus vs. Columnaris → Fungus = true fungal infection on dead tissue; Columnaris = bacterial, looks like “cotton” but needs antibiotics.
  • ✂️ Fin Rot vs. Aggression Damage → Fin rot shows tissue breakdown; aggression leaves torn, uneven bites.

👉 Misdiagnosis is common. Always test water first, then treat carefully.


🪣 Step 2: Quarantine the Sick Fish

  • 🚧 Move to hospital tank.
  • 🛡️ Prevents spread.
  • 💊 Allows targeted treatment.
  • 🧼 Keep simple: bare bottom, heater, sponge filter, airstone.

💧 Step 3: Test & Fix Water Quality

  • Ammonia → 0 ppm
  • Nitrite → 0 ppm
  • Nitrate → <20–40 ppm
  • pH → Stable
  • Temp → Appropriate for species

Bad water quality = stressed, sick fish.


💊 Step 4: Begin Treatment (Choose Carefully)

  • ❄️ Ich → Heat + ich medication.
  • 🦠 Epistylis → Antibiotics (kanamycin, furan-2).
  • 🍄 True Fungus → Antifungal meds (methylene blue, salt dips).
  • 🦠 Columnaris → Broad-spectrum antibiotics.
  • ✂️ Fin Rot → Water changes + antibiotics or antibacterial meds.
  • 🪱 Parasites → Praziquantel, copper-based meds, or metronidazole.
  • 🎈 Swim Bladder Issues → Fasting, peas, possibly antibiotics.

💊 Be Prepared: Stock a Fish Medicine Cabinet

Don’t wait until you see sick fish to order meds — by the time they arrive, it may be too late. Just like we keep aspirin for headaches or cough syrup for colds, your fish need fast relief too.

🧴 Recommended Medications to Keep on Hand

  • ❄️ Ich Treatment (malachite green, copper, formalin-based)
  • 🦠 Broad-Spectrum Antibiotic (kanamycin, erythromycin, furan-2)
  • 🍄 Antifungal (methylene blue)
  • 🪱 Anti-Parasite Meds (praziquantel, metronidazole, copper)
  • 🧂 Aquarium Salt (general support, mild infections, stress relief)
  • 🌿 Stress Coat/Dechlorinator (improves slime coat, reduces stress)

👉 Having a well-stocked fish medicine kit allows you to start treatment immediately and saves precious time when fish are at risk.


🍽️ Step 5: Supportive Care

  • 🌑 Dim lights to reduce stress.
  • 🚫 Remove uneaten food.
  • 💨 Boost aeration.
  • 🌡️ Keep temperature stable.
  • 🍲 Offer vitamin-rich, high-quality foods.

🕒 Step 6: Monitor Daily

  • 👀 Watch for improvement/worsening.
  • 🐟 Check other fish for symptoms.
  • ⏳ Finish full treatment course.
  • 📝 Keep notes for future reference.

🛡️ Prevention Tips

  • 🪣 Quarantine new arrivals (2–4 weeks).
  • 💧 Weekly water changes (20–50%).
  • 🚫 Avoid overcrowding.
  • 🍽️ Don’t overfeed.
  • 🧼 Sterilize equipment between tanks.

📝 Quick Symptom Confusion Chart

Symptom Could Be Key Difference
⚪ White spots Ich OR Epistylis Ich = responds to ich meds. Epistylis = bacterial, needs antibiotics.
🦠 Cotton patches Fungus OR Columnaris Fungus = true fungus. Columnaris = bacterial “cotton”.
✂️ Frayed fins Fin rot OR Aggression Rot = tissue decay. Aggression = bite marks/tears.
🫁 Gasping at surface Oxygen issue OR Gill Flukes Test water first. If clean → parasite more likely.

⚡ Golden Rule:

  1. Test water first.
  2. Quarantine if possible.
  3. Treat with the correct medication.
  4. Keep a stocked medicine cabinet so you’re always ready.

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