Well from my reading the hydrated lime does not last long...meaning much over a month. Its a quick swing, then settles quickly. I may be wrong, that is what I have gathered from my reading. Now ag lime on the other hand will stay and last having an effect over a long period of time, changing pH slowly with a max of like 8.4 I think. Please correct me if I'm wrong.

HalfAcre, thats exactly it. Its been such a struggle to get the pond to where it is, I hate to drain...I love the idea of draining and having fresh water and starting over the correct way...but if it turns off dry, I could be years before my current level is ever seen again.