Nick,
Although 230 does seem like alot, we are still under the max rate for grass carp here in PA.
Before we stocked them, our 15 acre lake was 95% covered from the bottom to the surface with Niaid and Curly Leaf Pondweed.
After 2 years we still have plenty of weeds. I don't think that they are going to go hungry anytime soon.

Buckshot