1. PH ranges from 0 ——- 14
2. 7 is the neutral point
3. Below 7 is acidic
4. Above 7 is alkaline
5. No discus fish should be kept in water with pH lower than 5 or much higher than 7.5
6. Discus fish will stay happy at the pH value of between 6 to 6.8
7. Most of the discus fish should be able to tolerate a slight change of the pH value of the water, as long as the change is gradual
8. In breeding, the discus fish prefer acidic water
9. To check the pH value is monitored by means of pH-testing kit or electrical pH meter, which is the most accurate.
10. The above is also apply to the tropical fish other than the discus fish.