I applied a dose of Sonar RTU last year in my pond and it knocked out the duckweed till today. I noticed a few sprouts around debris in the water, not much.
Now the thing is, I shut off my aerator 2 days ago to see if it helped with water clarity. So I'm wondering if it's related to that. I hate to dose up the water if I don't have to (since it killed everything), but even more than that I hate the thought of having duckweed again.
I figure my options are: 1) nuke the duckweed again with a full dose of Sonar, 2) try a smaller dose, 3) wait and see if the aeration back on is enough to keep the duckweed at bay.
Incidentally I'm planning a alum dose the next time I have a few hours of free time (which could be 2 weeks out). I'm wondering if that may also help knock down the phosphorus enough to keep the duckweed in line. My phosphorous levels are at about 0.05 ppm so a bit high.
