Ha ha ha, we had that same pic in our science book back in school!
on a different note:
my neighbor has a pond about this size, his pond guy told him bottom aeration will cure problems like this and reduce muck. His reasoning, the sediment will float toward the overflow pipe and work its way out that way. get rid of that and the algea goes away. Does this sound feasible or is he just trying to sell an unecessary product?
I'm going to put in marginal plants..... any suggestions on good ones? Use some type of algecide on the falls itself
nothing but a horse and buggy