There are no underwater plants. I don't have any plans or desire to fertilize - too nervous. I don't know alkalinity. I am ordering a water testing kit this week.

Any idea if the stuff in the white bucket is harmful? I skimmed that stuff off the top of the lake where you see all the bubbles and white stuff in the other pictures. I brought it home and put it in a jar full of lake water. On the lake it is floating. In the jar it has all settled to the bottom which I thought odd.