I'm trying to control watermeal on a 3.5 acre pond with bass and bluegill. I'm reluctant to use chemicals. I was told by a fish source that Japanese koi would control watermeal by eating it and reducing nitrates in the water. Can anyone verify any results?

Also I've read tilapia may work but will not survive the INDIANA winters. Any experiences?

Lastly, it seams the only proven option is sonar. What is the minimum concentration that gives results?

Thanks in advance.