Bill, To answer your question I not only have heard about hydrated lime, but applied it several times.

I'm going to mention Ken again since your familiar with him. His "slack lime" is simply hydrated lime at three times the price. He sells that and then he tells you need his calcium buffer. All of this is true. It works great, jumps the hardness and more importantly the alkalintiy way up. Bad thing as Shan mentioned it is gone after a few good rains. I have seen many clients that have spend over $10,000 in only two year with this method to currently have a alkalinity of only 10 ppm.

Hydrated lime is Calcium hydroxide CaOH. AG lime is calcium carbonate. Hydrated lime is very basic (high pH) and if applied at more than 100 lbs/ac can lead to a fish kill. I use it when good old ag lime can not be applied to the pond. I used to apply with my old company three times a year at the lake between the Doubltree hotel (King and Queen) What a pain! I currently use it on three ponds we have great results with it when done properly, but if possible 4 tons/acre ag lime is the way to go. Hope this helped to clear this up.

Greg Grimes
www.lakework.com