Grass carp, or white amur are great tools to remove vegetation safely from ponds and lakes. However, they aren't perfect. There are some plants they don't like, like coontail, so higher stocking densities are required. Some plants they physically can't eat, like filamentous algae. You know, the stuff that floats around in mats on the surface in late spring/summer. Finally, they are indiscriminant in their eating, and may give you more control than you need.
Chemicals have their place. They are good for spot treating shoreline areas that you want to fish. They treat vegetation that nothing else will work on. Some states don't allow grass carp and so chemicals are the only option in large areas. I agree with PineRidge that there are certainly better options than copper sulfate, although almost all of them are more expensive.
Manually removing weeds is difficult and will only work in small areas.
If anyone has any specific questions, they are always welcome to PM me. Most problems have similar solutions, whether you are in Virginia, California, or Texas. /forums/images/graemlins/smile.gif