Here are some more pictures showing just how green my koi pond got, and one of the large frogs that is inhabiting it.  We have a number of large frogs this year - more than normal and they are larger than normal.  I like the frogs, but they tend to hide and jump out when I lift up the cover to the filter - scaring both of us.  I'll get pictures of the "clean" pond today to show what can change in a week!