Keep in mind that the more alum that is applied per acre foot of water the more the need for buffering of lime or natural lime carbonates. I have applied alum in ponds with fish and Higher alkalinity and hardness (100-250ppm, mg/L) and found it will buffer most suggested applications of alum (100-400lbs/ac) without the need for lime addition. Below 90mg/L alkalinity, I suggest you monitor the pH when adding alum.
As already noted: after - during alum application, there is a chemical reaction that impacts the pH (acidity) of the water. The reaction produces small amounts of sulfuric acid which can decrease pH significantly in some lower alkalinity buffered waters to levels harmful to aquatic life. You can treat with a suggested or minimal amount of alum and wait a day or two to determine if more alum is needed to achieve water clarity 18"-2ft. Therefore, alkalinity and pH should be tested prior to application. Alkalinity should exceed 100 mg/l and pH should be greater than 7.0.
Last edited by Bill Cody; 03/16/1710:54 AM.
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