pH is literally “potential hydrogen” or “power of hydrogen.” Water pH for fish farms and hatcheries in more specific terms is a measure of acidity or alkalinity of water for farming and hatchery purposes. It refers to the concentration of hydrogen ions (H+) or hydroxyl ions (OH-) in water. pH value for any medium can assume a number from 1 to 14.
A pH value less than 7 indicates acidity, while one greater than 7 indicates alkalinity. The further less than 7 a pH value gets, the more acidity it indicates. Increasing alkalinity aligns with increasing pH values from 7 to 14. A pH value of 7 indicates neutral pH of the medium (water in this case).
Pond water pH for fish farms and hatcheries, is a function of carbon dioxide concentration and mineral composition of pond, well or borehole and surrounding soil. The pH of fish pond water may thus increase during the day as photosynthesis takes place and carbon dioxide is used up. The converse is the case during the night when photosynthesis stops and carbon dioxide builds up.
Optimum pH for most fish species falls within 6.5 – 9 and very pronounced deviations from this range may cause fish production to reduce significantly and in extreme cases, lead to fish mortality.
pH of water can be measured using electronic pH meters (that give pH values in direct digitally readable figures) or with a colour spectrum calibrated pH test kit – the lovibond comparator. pH test strips also employ similar mechanism.
Litmus papers also give a quick indication of the pH of water in contact with them. Acidity of water, like other media, causes blue litmus papers to turn red, while alkalinity causes red litmus papers to turn blue.
Neutral media yield no noticeable change in colour on litmus papers brought in contact with them.
The lovibond comparator provides an array of colours, each of which corresponds to specific pH values on the pH scale (0 – 7 – 14).
pH test strips come with an indicator (usually a liquid chemical) which when reacted with the liquid medium to be tested, turns it into a colour that matches one of the array of colours displayed on the lovibond comparator. pH value corresponding to that colour can thus be picked by physical observation.
Ovie, 1986 published that high pH (alkalinity) of water can be corrected using aluminium sulphate (alum) or calcium sulphate (gypsum). Low water pH on the other hand can be corrected using lime. Quicklime, slaked / hydrated lime, agricultural limestone and soda ash are examples of lining materials that are commonly used.