One of the most important groups of bases which will register on a total alkalinity test are the carbonates. Carbonates serve as a buffer for pH in water. In a pond with low carbonate levels, carbon dioxide can cause rapid changes in the pH. During the day, carbon dioxide levels in ponds are typically low, or non- existent. Algae in the water use carbon dioxide as quickly as it is produced in the process of photosynthesis. In cases with extremely low carbonates, daily fluctuations in pH levels can be severe, causing other problems in the water quality of the pond.
Limestone is calcium carbonate, and dolomite is a mixture of calcium and magnesium carbonates.
By adding crushed limestone or dolomite to a pond, you can increase the carbonate and total alkalinity of a pond. Total alkalinity levels in a pond should be above 50 parts per million. If you measure the total alkalinity and it is less than 50 parts per million, add crushed limestone or dolomite at a rate of about one ton per surface acre. Buy the finest grade of limestone available, as it will dissolve in the water better than a course grade. Total effect of liming will not be measured for several weeks, as it dissolves slowly into the water column.