pH?

(see also "Acid Test") Neutral water is given a pH value of 7.0. It contains equal amounts of hydrogen ions (H+) and hydroxide ions (OH-). Dissolved chemicals and minerals change the balance of those ions from a perfectly neutral state. Increase the amount of hydrogen ions (H+), and the water becomes more acid ("low pH"). Increase the amount of hydroxide ions (OH-), and the water becomes more alkaline ("high pH"). The further these values rise or fall, the more acid or alkaline the water becomes.

 
   
Normal pH?

There is no "normal" pH. As fish originate in surroundings that have different pH levels, their needs can differ. Saltwater fish prefer an alkaline pH of 8.0 or above. Freshwater fish prefer a pH between 5.5 and 7.5. pH changes as new fish are added or removed or as water is added.

 
   
What is a buffering capacity?

Buffering capacity refers to water's ability to keep the pH stable as acids or bases are added. pH and buffering capacity are closely connected to another. If the water has sufficient buffering capacity, it can absorb and neutralise added acid or base without significantly changing the pH.

 
 
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