1. The Dead Fish Should Be Removed from the Aquarium Immediately

• Dead fish decompose quickly and increase ammonia levels.

• This creates a toxic effect for the other fish.

• As soon as a dead fish is noticed, it should be removed with a clean net and disposed of hygienically.

1. Try to Understand the Cause of Death

• If the fish’s behavior before death was observed, take note of it.

• If there are signs such as wounds, fungus, spots, or swelling on the body, the likelihood of disease is high.

• Check whether other fish show similar symptoms.

• Review recent changes such as water changes, feeding habits, or the addition of new fish.

1. Water Quality Should Be Checked

• Ammonia, nitrite, nitrate, and pH levels should be measured with a test kit.

• If necessary, perform a 25–30% water change.

• Ensure the filtration system and air pumps are functioning properly.

• Do not neglect gravel cleaning and filter maintenance.

1. Other Fish Should Be Monitored and Quarantined if Necessary

• If other fish show symptoms, affected ones should be quarantined in a separate tank.

• In cases of visible parasites, fungus, or infection, appropriate medication should be started.

• The behavior of the observed fish should be monitored daily.

1. Is There a Risk of Disease?

• Yes, especially if the dead fish is suspected to have died due to parasites or bacterial infection, the other fish are also at risk.

• Some diseases can spread even without direct contact between fish (e.g., ich/white spot, internal parasites).

• Therefore, preventive medication may be required (consultation with a vet or expert is recommended).

1. Preventive Measures for the Future

• Perform regular weekly water changes.

• Ensure the fish live in conditions suitable for their species.

• Do not add new fish to the main aquarium without a quarantine process.

• Provide a balanced feeding program and avoid overfeeding.

• Regularly observe aquarium inhabitants and track behavioral changes.

Conclusion
The death of a fish in an aquarium is not just the loss of one life, but a warning that the entire system should be carefully evaluated. With timely intervention, proper analysis, and preventive care practices, you can protect the health of existing fish and prevent similar losses in the future.