Total AlkalinityTotal alkalinity is the total concentration of bases in water expressed as parts per million (ppm) or milligrams per liter (mg/L) of calcium carbonate (CaCO3). These bases are usually bicarbonates (HCO3) and carbonates (CO3), and they act as a buffer system that prevents drastic changes in pH. For example, in waters with low alkalinity, pH might fluctuate from 6 or lower to as high as 10 or above; while in high alkalinity waters, pH might fluctuate from about 7.5 to 8.5. Greater production in bass-bluegill ponds is attained in high alkalinity waters because this pH buffering capacity makes phosphorus and other essential nutrients more available to the algae bloom. Total alkalinity is not the same as hardness. Calcium (Ca++) and magnesium (Mg++) are primarily responsible for hardness. However, in most waters, alkalinity and hardness have similar values because the carbonates and bicarbonates responsible for total alkalinity are usually brought into the water in the form of calcium carbonate or magnesium carbonate. Waters with high total alkalinity are not always hard, since the carbonates can be brought into the water in the form of sodium or potassium carbonate. Improving AlkalinityThe most common method of increasing alkalinity in waters is by adding agricultural limestone (calcium carbonate). Fish managers in Europe and Asia have reported that applictions of lime to fish ponds on soils of low calcium content resulted in greater fish production. Fish managers in the United States showed that applications of lime to lakes increased pH and total alkalinity and also cleared water of brown stain from humic substances. Clear water results in deeper light penetration and greater photosynthesis, as well as increased zooplankton production. Fertilization does not produce adequate phytoplankton (algae bloom) in many ponds with soft waters and acid muds because carbon dioxide is in short supply, and added phosphate adheres tightly to the bottom muds. Addition of lime to these ponds elevates total bicarbonate alkalinity and increases pH in the water. Neutralization of bottom muds with lime prevents phosphate from adhering to it, thereby increasing phosphorus concentrations in the water. As a result of these changes in water quality, phytoplankton blooms develop upon application of inorganic fertilizers. Liming soft water ponds to increase alkalinities to at least 20 ppm is beneficial to fish production. As a general rule, ponds with alkalinities less than 20 ppm do not respond well to fertilization and should be limed in the fall before springtime fertilization is initiated. Liming ponds with alkalinities greater then 20 ppm typically will not increase the response to fertilizer. It does, however, increase the alkalinity and pH buffer capacity. Copper Sulfate
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