Thanks for the photos. It seems my pond is always in bloom but it definitely goes through many various shades of green and occasionally brown - brown doesn't last long. My pond was a stock tank before I bought the place and I have always wondered if the years of cows, horses, and manure have made it so nutrient rich it just isn't going to get very clear. I am going to build a secchi disk and see what that tells me. I have always backburnered it because I am just not sure what can be done if the problem is decades of nutrient build up - a bit of head in the sand syndrome. Aeration seems to have helped some but I may just be seeing that because I want to see it. I have some BG with fish eye fluke but beyond that the fish seem healthy and are visibly getting healthier and the pond looks nice and definitely adds (instead of subtracts) from the aesthetics of our place. But, the budding pondmeister in me worries about the mysterious plankton bloom. I am glad this thread came up.