Troubleshooting Common Fish Issues

Troubleshooting Common Fish Issues

Even the best-kept aquariums occasionally run into problems. If your fish seem off — hiding, not eating, or showing strange behavior — this guide will help you quickly diagnose and resolve the most common freshwater fish issues. Acting fast can save lives and restore balance to your tank.

🐟 Common Warning Signs

  • Loss of appetite
  • Clamped fins
  • Erratic swimming or flashing (rubbing on decor)
  • White spots, redness, cloudy eyes, or fin damage
  • Hiding constantly or breathing heavily near the surface

If you see any of these, begin by testing your water immediately.

🧪 Step 1: Check Water Parameters

  • Ammonia: 0 ppm
  • Nitrite: 0 ppm
  • Nitrate: under 40 ppm
  • pH: stable, based on species needs
  • Temperature: 74–80°F for tropical tanks

Even slightly elevated ammonia or nitrite can cause stress, illness, or death. Perform a 25–50% water change if levels are off.

🔍 Issue: Fish Gasping at the Surface

Cause: Low oxygen, high ammonia, poor circulation

Fix: Increase surface agitation with a bubbler or raise filter output. Do an emergency water change. Check for clogged filters or overcrowding.

🔍 Issue: White Spots (Ich)

Cause: Ichthyophthirius multifiliis — a common parasite triggered by stress

Fix: Raise temp to 82°F, treat with Ich-X, salt, or copper-based meds. Treat entire tank. Quarantine new fish next time.

🔍 Issue: Fungus or Cotton Growth

Cause: Fungal infection or columnaris bacteria

Fix: Use an antifungal like Pimafix or antibacterial like Maracyn. Isolate affected fish. Improve tank hygiene and filtration.

🔍 Issue: Red Streaks or Open Wounds

Cause: Bacterial infection or injury

Fix: Add antibacterial treatment (Kanaplex, Maracyn 2), improve water quality, isolate injured fish

🔍 Issue: Fish Not Eating

Cause: Stress, illness, improper water parameters, or bullying

Fix: Test water, offer frozen/live foods, reduce lighting, remove aggressive tankmates

⚠️ Preventative Tips

  • Quarantine new fish for 2–4 weeks
  • Don’t overfeed — excess food = dirty water
  • Keep a consistent maintenance schedule
  • Test water weekly, not just when something’s wrong
  • Observe fish daily — behavior changes are your early warning system

Many fish issues can be resolved quickly with proper diagnosis and fast action. Still unsure? Send us photos and water test results — we’re happy to help you troubleshoot directly.