I've searched the world over looking for powdered alum, and nada. All I could find in my area is alum crystals in 15lb bags. The stuff looks like salt. I've mixed a teaspoon in 1/4 cup of water and once it finally dissolves, it's clear, not a slurry. I added that to 1 gallon of my muddy pond water and after a day it's as clear as tap water. So, I'm sure this should work, but now my question is, what ratio do I use in mixing? Is it the same as the powdered alum? I've bought 250 lb of this stuff (at $1/lb) that I'll be picking up today. I'll be mixing it in a 50gal drum (40gal at a time) and spraying it from the banks. How much should I put into each 40gal mix? Isn't it possible that I could put so much alum in the drum that it will never dissolve? It took a long time to dissolve 1 teaspoon in 1/4 cup so I think I'll be spending most of my time with the boat prop in the drum. Any advice?