pH is a measure of acidity/alkalinity in water. 7 is considered to be neutral pH. Any pH reading above 7 is considered to be alkaline, while a pH reading below 7 is acidic.
Generally, pH levels ranging from 8.1 to 8.4 are acceptable in saltwater aquarium tanks. But, for reef tanks the optimum pH levels need to be more towards the higher levels. There are certain factors that normally contribute towards a low pH level within the reef tank. These factors include acids which are natural by-products of the life processes that take place within a tank. Some of the most important acids include: Carbon dioxide, nitric acids and organic acids. Carbon dioxide is released regularly due to the respiratory processes of fish. Collection of nitric acid is due to biological filtration. Metabolic wastes of the fish leads to a collection of organic wastes in the water which turns acidic.
The pH in a tank needs to be monitored on a DAILY basis to ensure that it is stable and within the desired limits. The easiest way is to add some baking soda, or bicarbonate of soda into the water. There are a number of other buffering products available.
The best method of reducing acid build up within the tank is regular water change and is most effective in controlling the pH of reef tanks. The next best method is filtration.
If the pH reading in a reef tank fluctuates wildly, this shows that certain water parameters may be endangering the life of the inhabitants in an aquarium.
Hence, use of pH Meter indicators to monitor the pH becomes very important. You can also use pH Controllers which will automate the process of adding alkaline additives to keep the pH in check !