How to do a water change effectively in an aquarium?

To do a water change effectively in an aquarium, follow these steps:

1. Prepare new water by treating it with a water conditioner to remove chlorine and other harmful chemicals.
2. Use a siphon to remove about 25-50 of the water from the aquarium, depending on the tank's size and the water quality.
3. Clean the gravel or substrate while siphoning to remove debris and waste.
4. Pour the new treated water into the tank slowly to avoid disturbing the fish and the tank's environment.
5. Monitor the water parameters after the water change to ensure the health of the fish and other aquatic life.