re: Pond Clarity

quote:

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Also, make sure its POWDERED gypsum, not pelletized.

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This. Gypsum is the safest coagulant to use as it will not alter the water chemistry other than increasing water hardness which is not an issue.

Alum (Aluminum sulfate) is the most effective turbidity coagulant but there is potential danger in dropping water pH to low (too acid) unless the pond water has sufficient alkalinity (buffering capacity).

It’s also important to note that there are different types “lime” - agricultural limestone (calcium carbonate), slaked lime (calcium hydroxide) & burnt lime or quick lime (calcium oxide). Slaked lime and burnt lime should rarely be used in fish pond management has they can increase water pH to levels that can kill fish. Agricultural limestone is the product of choice, but the least effective product for coagulating turbidity and “clearing” up ponds. Agricultural limestone has very low water solubility.

Some literature

Control of Clay Turbidity in Ponds

Clearing Cloudy & Muddy Water in Ponds & Lakes