I guess now I am wondering why you want to apply Alum if you have no colloidal clay issues....are you wanting to bind available phosphorus in the pond?
Snipe,
Did you answer this question and I just missed it?
Another question, have you had your water tested to determine it's alkalinity? My understanding, and it is limited, is that if the alkalinity is high enough in a BOW, there may be no need to add the hydrated lime as the water can buffer the Alum treatment on its own. Have you tried adding Alum to a water sample to see the impact on its Ph?
Sorry if I'm "muddying the water" with my questions......just trying to learn