pH
Desirable Range 6.5-9.5
Acceptable Range 5.5-10.0
The pH of water is a measure of how acid or basic it is, on a scale of 0 to 14 with 7 being neutral.
In fish ponds, the time of day that a sample is taken often will influence the pH because of variations in the carbon dioxide (CO2) concentration. As plants in the water remove carbon dioxide for photosynthesis, the pH will increase.
At night, the pH will decrease as carbon dioxide accumulates.
Increasing the total alkalinity concentration in water helps buffer against pH changes.
Most fish species do well within the pH range of 6.5 to 9.5.
Chronic pH levels below 6.5 may reduce fish reproduction and are associated with fish die-offs that sometimes occur in the late winter.
Newly hatched fish (fry) are often sensitive to pH levels above 9.0 t o 9 . 5 .