Looks like Coontail or Eur Milfoil to me. A better way to identify it is take a small piece out and lay it on a blank piece of white paper, get a close up photo. I have a brand new customer with same problem. Either hitchhiked with a fish delivery or a aquarium dump. Probably going mechanical cut and carp at first.
Bear in mind there have been a few threads lately where people have had less than desirable results with grass carp. It is iffy at best.
Last edited by The Pond Frog; 04/28/10 10:58 AM.