A buffering agent helps prevent a rapid change in pH of a solution when other substances are added or mixed with the solution. For example, most shampoos are buffered so that they are slightly acidic. The buffer counteracts the alkalinity of soap. If either of these substances become too acidic or too alkaline, they could damage your skin and hair.
Human blood pH should be slightly alkaline (7.35 – 7.45). Below or above this range would cause symptoms and disease. If blood pH moves below 6.8 or above 7.8, cells stop functioning and the body dies. The body, therefore, continually strives to balance pH. Many forms of life will survive only within a relatively small pH range so they utilize a buffer to maintain a constant pH.
Another example of how a buffering agent is commonly used is in aspirin. Without buffering, aspirin can irritate the lining of the stomach and lead to serious medical conditions such as bleeding and ulcers. The antacid properties of buffering agents are thought to help maintain the pH balance and and may help prevent side effects. Whether aspirin buffers actually work is still controversial.
The most common problem with aquarium water chemistry is pH. Although most fish will thrive in a wide range of pH, rapid changes may cause stress leading to disease or death. Though some exotic fish such as Discus are more particular about pH, even most of these fish are only particular about pH when they are breeding. The fish will not spawn if the proper pH is not maintained. There is a growing trend to believe that the pH in a fish tank needs to be around 7.0 which in most cases in simply not true for fish. However, in aquaponics, we also have to consider the pH requirements of the plants. Plants, in general, in water that has a lower pH than ordinary tap water.
If your tap water contains buffers, and almost all tap water does, it probably keeps the pH around 8.0 or slightly alkaline. This can make it difficult to lower the pH in your tank. The water will maintain a high pH because of the buffers. You will need to add enough acid to neutralize the buffer. However, by the time you have added enough acid to overcome the buffer, you will have enough acid in the water to cause a precipitous drop in pH.
Water has a pH of 7 naturally, but the water you are using in your tank may be different because of the chemicals that are suspended or dissolved in the water. These chemicals fall into three categories: acids, bases, and buffers. Acids are chemicals that lower the pH, or make the water more acidic. Bases are chemicals that raise the pH of the water, or make it more basic (or alkaline). Buffers are chemicals that can prevent changes and keep the water at a specific pH. Different buffers will keep the pH at different values.
If you need to lower pH, you could add some type of acid. Muriatic acid is commonly used to lower the pH of swimming pools. If you need to raise pH, you could add a product that is alkaline such as sodium carbonate commonly know as soda ash.
In simplistic terms, a buffer would be something that has both acid and alkaline properties. When pH starts to rise, the buffer would release acid to reduce pH. If the pH begins to decrease, the alkaline agent would be released to increase the pH.
If you are Walter White (Breaking Bad), you will probably mix you own buffers. However, most of us will be better off buying a commercial product that is formulated to keep pH at a certain level. Seachem, for example, is one company that makes buffers that will work for most aquaponic applications.