Have a landlocked pond, spring fed with almost no runoff, covered with watermeal. I read grass carp would not work because they grow fast and
watermeal will go thru their lungs. Sense they have to be sterile in N.C. I can't raise them to get a constant supply of fingerlings. I thought of trying raise Tilapia in a small backyard to supply fingerlings for the big pond, wandering if anyone has tried this.

Chuck, my understanding is that tilapia focus more on algae than duckweed. However, there are real experts here who know more & I'm sure will give you the straight story.

Two points to remember: Make sure stocked tilapia are legal in yuor state (they aren't in every state), and they won't survive the winter outdoors, so you will need to restock every year.