white amur is the species. common name grass carp. highly vegetarian. any fish hatchery will have them , usually 8 bucks or so a piece. check with your state, here in va we have to apply for a permit to stock them.
Triploid Grass Carp are banned in WI. They also consume beneficial and native plants. Contact www.keystonehatcheries.com for algaecide for the Milfoil. They specialize in pond care for WI and IL.
Keep manually raking out the weeds. In early spring you can add pond dye and Sonar/Avast to control the weeds. Sonar is much cheaper and can be purchased in small quanities.