Alum Treatment in Sherwood Fingers and Coves

Regarding the question about applying the alum in shallow coves:


This is a common question and we are happy to provide some input.  The alum is different from herbicides/algaecides as it doesn’t “kill” the algae.  Alum works by chemically binding up the nutrient that is fueling excessive algal growth (Phosphorus).  In a sense, the algae is “starved” by lowering the amount of phosphorus available for growth.  So, the alum doesn’t need to come in direct contact with the algae to control it.


Our main goal at Sherwood is remove the phosphorus that is suspended in the water.  The vast majority of the water is in the main part of the lake and water in the canals exchange with the water in the main lake.  Therefore the alum is applied in the main, deeper portions of the lake where the majority of the phosphorus is located.  Applying alum in the canals would only bind a very small and insignificant portion of the entire amount of phosphorus in the lake.


John Holz, PhD

Senior Limnologist