1. Don't Panic, but Act Quickly:
* Isolate the fish: Immediately move your goldfish to a separate tank or container. This prevents the spread of any potential infection to other fish.
2. Identify the Cause:
* Fungal Infection: Fuzz could indicate a fungal infection. This is common in fish, and it can be caused by stress, poor water quality, or injury.
* Parasites: Parasites can also cause fuzz-like growths on a fish.
* Bacterial Infection: While less common, bacteria can sometimes cause a fuzzy appearance.
3. Get Professional Help:
* Visit a Fish Veterinarian: A fish vet can diagnose the exact cause of the fuzz and provide the appropriate treatment. This is the most important step.
4. Immediate Home Care (While Waiting for a Vet):
* Water Quality: Check the water parameters (temperature, ammonia, nitrites, nitrates) and ensure they are within safe ranges.
* Cleanliness: Perform a partial water change to improve water quality.
* Medication: A fish vet can prescribe medication for fungal infections, parasites, or bacterial infections. Do not attempt to treat your fish with medications without a proper diagnosis.
Important Reminders:
* Don't rely on online advice: Internet forums can be helpful, but a fish vet's diagnosis and treatment are crucial for your goldfish's health.
* Prevention is key: Maintain good water quality, avoid overfeeding, and monitor your fish for any changes in behavior or appearance.
I hope your goldfish recovers quickly. Good luck!