Little off subject but involves the fish . 25-30 years ago when there were giant largemouth in Browns lake in NT state park there were man made square corrals , for lack of better description , that contained many sacks of what I was told was fertilizer ? They were used to enhance the fishing . Now I hear people talk abt fertilizer draining into lakes is causing die off . Does anyone have experience in the use of fertilizer in their lake ? I have a spring fed lake filling as I speak and don't want to try something I'm not sure of .