Salifert pH Test Kit (Reef)The pH value can have a major impact on the growth of corals and calcareous algae and on many biological processes. The pH should not be allowed to fluctuate more than approx. 0. 3 units during 24 hours and should preferably be kept between 8. 0 and 8. 2. If the pH is too low then the cause may be a too low alkalinity and or insufficient aeration. A low pH can be corrected by improving aeration and by increasing the alkalinity to NSW (Natural