Here is a picture of my thought on an easy way to mix alum in water and spray it over a pond. Set the bucket in water nearly up to its rim either off the pond bank or over the side of a boat. Feed the dry alum into the water being sucked into the hose and it will get mixed as it runs through the hose, pump and out the nozzle. I have not done this but expect it to work. May need to add more holes to allow water into the bucket if I need it to run flat out without sucking in air.

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