All I can say is that is a problem I had with grass carp. They liked the feed more than the weeds, even though the species of weeds I have are right on the top of their list of preferred ones.

If you don't have a weed problem why put them in in the first place? If you have good bloom going that should keep your weeds down.

If pigs could fly bacon would be harder to come by and there would be a lot of damaged trees.