Main Reasons:
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Stress from a new environment: New fish introduced to the pond, excessive water changes, etc.
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External frights: Interference from cats, birds, electrical leaks, noise, etc.
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Health issues: Parasites, bacterial infections, or poor water quality.
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Human disturbance: Frequent netting, tapping on the pond walls, etc.
Steps to Take:
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Observe first: Check if the koi are rubbing against objects, gasping at the surface, or showing other unusual behaviors. Look for white spots, redness, or other signs on their bodies.
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Test water quality: Measure ammonia, nitrite, and pH levels to ensure they are within safe ranges.
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Check equipment: Verify there are no electrical leaks (use a voltage tester) and look for signs of animal interference nearby.
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Address the cause:
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If water quality is poor → Change 1/3 of the water and improve filtration.
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If parasites are suspected → Take a sample for microscopic examination and treat accordingly.
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If environmental stress is the issue → Add vitamin C (2–3 mg/L of water) and provide hiding spots.
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Build trust: Feed at the same time and place each day, avoid sudden movements or loud noises, and gradually reduce your distance from the fish.
Important Notes:
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Avoid frequent netting or forced interaction.
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Do not use sedatives unnecessarily; prioritize improving the environment.
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Consider installing cat‑proof nets, bird deterrents, etc., to reduce external threats.
