What about carp (if someone wanted to stay away from chemicals)? I have seen success with small carp (double the normal stocking rate) and duckweed. Watermil and duckweed can almost be seen multiplying under the microscope (bad stuff). If the carp can get an initial handle on the problem, then you could eliminate the chemical application ($), and provide a safer ecological alternative.
Just another random thought for the day, but I would like other's opinions as I too am learning a lot about water management.
BTW Pondfishr your pond is beautiful. You notice how the surface aerator is pushing the "green stuff" away. Strong winds and currents do this. You are lucky to have pond this size. It might be possible to set your aeration system up so that most of your topwater problem is "pushed" to one area. That would make things easier to control via carp, tilapia, or chemicals.
If your nutrient levels are already high enough (no fertilization needed), the answer MAY be as simple as adding some more carp and or tilapia (per state regulations), moving over your aerator slightly, and adding pond dye ONLY when things start getting dense (mid-summer). You want to keep a good plankton level in your 18-24 inch water column, but anything thicker than that can cause adverse reactions in late summer. As the plankton gets extremely dense it will consume oxygen during the night (die off) possibly resulting in a fish kill (or at the very least fish stress).
All back to goals and management!
