* Water quality: Fish waste and uneaten food can pollute the water, even with only one fish. Changing some water helps maintain water quality and keeps your remaining fish healthy.
* Stress: Losing a tank mate can be stressful for the remaining fish. A clean environment can help reduce stress.
How to change water:
1. Remove about 25% of the water from the tank using a siphon or bucket.
2. Replace the removed water with dechlorinated water that's the same temperature as the tank.
3. Test the water parameters (ammonia, nitrite, nitrate, pH) after the water change and make adjustments as needed.
Additional tips:
* Observe your remaining fish closely for any signs of illness or stress.
* Clean the gravel and any decorations in the tank to remove debris.
* Check the filter and clean it if necessary.
By changing the water and keeping the tank clean, you can help your remaining fish stay healthy and happy.