Sara, I think the reason you haven't gotten more responses from the experts is that they are having a hard time picturing your scenario. I know I am. Can you describe the size, depth, previous stockings and when? Any other thing about the pond you can supply. Surface aeration? Maybe Bill Cody or one of the other aquatic vegetation pros will read it this weekend. I doesn't sound like the alum killed a plankton bloom, as you said it is still green. Can you describe or take a pic of the stuff you are taking out? It would really help.
