Hobart, I had green water problems also. It seems that you have two choices. You can find a lab to do the testing and quantify your results or, you can just wing it and guess at the correct application rate until you get the desired results. I applied half of the recommended amount and re-tested to confirm its effectiveness. I have used phoslock and phosclear and have had good results with both. The alum/hydrated lime application that was done on my pond was for a suspended clay issue and worked very well for that. None of these options are cheap. I still have a small patch of FA here and there but it is not a problem. Eliminating the P source seems to be the best medicine.
