I have a 5 acre pond, well water fed, no outflow. Have had a reoccuring elodea problem each summer, treated with a contact killer and Cutrine Plus. This year tried Sonar Q. Distributed 120 pounds May 1st. Water tested 11.6 ppb mid June. Added another 30 pounds of Q for insurance mid June. Mats of elodea have come to the surface with approx. 15 bleaching. Remaining elodea within the mats still green and healthy looking. Has anyone had experience that would help me? Thanks.

50 sterile grass carp should do the trick nicely I would think... That gives you a 10/acre density, and while you won't see much difference this year, after the stuff dies back in the winter they should be able to keep up with it next spring.