Most tropical fresh water fish live in water with a pH value of between 6.5 and 8.5 - some species are sensitive to pH values, while others are more flexible in their requirements. Check reference books for specific details.
If the pH reading is too high, then add pH down solution and re-test after an hour. If the pH is too low, then a partial water change is required.
It is recommended to test pH once per week.
