Water changes for an aquarium
The frequency of water changes and the amount of water to be changed in an aquarium depends on the following factors:
1. number of fish in your tank
It is better to keep the tank a little understocked since
a. there is more space for the fish to swim and grow
b. a smaller amount of pollutants are produced
c. fewer water changes are needed
2. the type of filtration used
3. The amount of fish food and debris.
For a fully stocked aquarium with adequate filtration, 25% of the water should be changed weekly. If the aquarium has only a few fish, the water may be changed every two to three weeks, as this reduces the stress on the fish. If the fish are overfed, the excess food will settle at the bottom of the fish tank and it will have to be cleaned more often.