I have three ponds and I saw that I was getting duck weed as well, I bought sterile carp four or five of them per Acre of pond. It has helped immensely.

By far the best way to stop duckweed that I've seen is to just dye the pond. My father-in-law's pond was thick with the stuff and he dyed it blue and the duckweed is gone. Doesn't hurt the fish and it's still safe to drink and swim and stuff because most dyes are supposed to be food grade but it makes it so that the less light reaches down in so that if duckweed grows it can only grow in the shallows.

You could have just pumped that water out.

Put tilapia in your pond, they eat duckweed and azola

Too much FERTILIZER on your beautiful green lawn behind the pond! You keep feeding the aquatic plants every time you sprinkle your lawn!

your lucky it didnt wash away your tread lines