What is Alkalinity?
Alkalinity is a measure of the pH buffering capacity of water. (In this case alkalinity is not used in the chemistry context, as alkalinity is typically used to indicate that the solution has a pH above 7.0, i.e. it is basic or alkaline). It indicates the concentration of carbonate (CO3)2-,hydrogen bicarbonate (HCO3)-, borate (BO3)3-, sulphate (SO4)2-, and hydroxide (OH)- anions.The actually value is determined by the amount of free acid, hydrogen ions (H+), required toneuralise all of the above anions.
Why is alkalinity important?
Alkalinity is what provides the correct and stable pH for a reef aquarium, if maintained at sufficient levels. A correct and stable pH, i.e. nonfluctuating, is important for the health of an aquariums inhabitants. Many authors state that alkalinity is important as it is a measure of the ability to resist a drop in pH. This is true, but it is only half of the story. It is also a measure of the ability to resist an increase in the pH, i.e. the “buffering” of the water works in both directions. Some components of the alkalinity buffer system are also utilized by organisms, such as hard corals, and so have to be present in sufficient amounts for good health and growth.Additionally, the higher the alkalinity, the greater the ability of the system to absorb the addition of an acid or a base with only small change in the actual pH.