Shorty, I've been considering doing an alum treatment on my pond as well and know a source I can get it for a fair price. Let me know if you're interested and we could put an order together.
Send me a PM and let know how much per 50# bag and what type. What I have on hand is "standard ground", I just made sure that I mixed it very well before putting it in the pond.
http://www.seedranch.com/Aluminum-Sulfate-Standard-Ground-50-lbs-p/aluminum-sulfate-standard.htm
