You don't need to understand the chemistry involved, but you should know the parameters affecting your finned friends. Most fish can adapt to life within a specific pH range. They'll tolerate gradual changes, but pushing the limits can cause illness.
The pH of a substance relates to the amount of hydrogen ion present. The pH scale measures pH from 1 to 14. A pH of 7 is neutral. Values of less than 7 are acidic and those greater than 7 are alkaline.
When the pH is Too Low or High
When the pH drops, fish may display abnormal swim patterns and behavior. A change in pH greater than +/- 0.3 in a 24-hour period can stress fish and make them more susceptible to diseases; therefore, any change in appearance may be due to something other than the pH level. Weekly water changes can help restore low pH balances to acceptable levels for your fish. Mineral leaching from limestone rocks or coral may cause alkaline increases. Adjust your tap water's pH according to your pets' preferred range. Commercial pH buffers can help. Then monitor the pH weekly. If it fluctuates, a simple water change may get it back into balance. If your fish do get sick , they may need other treatments.