Hey Mike
Im no pro but in my situation it has gotten worse each year. When I got my pond 3 years ago there was barely any pondweed, each fall it has gone down some, then the follow spring come back twice as bad. Im in the Shenandoah valley in va so it does freeze over. I don’t know this but I think the previous owner put allot of chemicals in there to keep it clean, and im gonna give that a shot myself just to knock it down some. how many grass carp are you putting in? I will be interested to hear how you think there doing, im thinking about putting some in this fall for a long term solution. The guys ive talked to locally who supply grass carp recommend anywhere’s from 3 to 12 per acre,, but they are selling the fish