Grass carp eat a wide variety of aquatic vegetation, reports Environmental Laboratory. As fry, grass carp consume plankton and soft plants. As they get older and larger, they consume a wider range of tougher aquatic vegetation.
Grass carp are used to control vegetation in ponds and alter the ecosystem of ponds. If populations are sufficiently high, grass carp tend to stimulate phytoplankton blooms that reduce water clarity. Ponds stocked with grass carp tend to have fewer ducks and bass in them. In some ponds, grass carp control cattails and bulrushes, but not in all ponds.
U.S. Geological Survey reports that grass carp prefer quiet, shallow waters and usually do not travel far. Grass carp are also called the white amur and can weigh as much as 70 pounds. Originally from Asia, grass carp were imported to Arkansas in the 1960s to control weeds in ponds and aquaculture facilities. Grass carp escaped and are established in many waters in the United States, having been found in 45 different states. The impact of grass carp on ecosystems is complex, but it is clear these fish can profoundly alter the ecosystem of any waterway by removing and altering the vegetation in the waterway.