pH
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pH is a relative measure of alkalinity and acidity, it's an expression of the number of free hydrogen atoms present. It's measured on a scale of 1 to 14, with 7 indicating neutral - neither acid nor base; lower numbers show increasing acidity, whereas higher numbers indicate more alkaline waters. Blood (pH of 7.5), seawater (9.3) and household ammonia (11.4) are all alkaline or basic; urine (6), oranges (4.5), Coca Cola Classic (2.5) and the contents of your stomach (2) are acidic. pH numbers represent a logarithmic scale so small differences in numbers can be significant: a pH of 4 is a thousand times more acidic than a pH of 6. Most species of life have a specific pH range in which they can survive. A wide variety of aquatic animals prefer a range of 6.5-8.0 pH. If pH is altered beyond an organism's normal range it will suffer and soon die off. Many pollutants push pH readings toward the extremes of the scale. A change of more than two points on the scale can kill many species of fish. Low pH can also allow toxic elements and compounds to become mobile and "available" for uptake by aquatic plants and animals.


Observations made on Stream Team about pH: