I disagree i have all kinds of plants in my pond with the koi. yes they like to flip rocks but they don't dig deep unless they get a taste of a root. Yellow and peacock iris . for get me nots, 5 types of lilly, Egyptian palm. frog bit, black taro, parot feather, hornwart, pickerel rush are all in the pond and they koi have got to a couple of them and i just built stone walls around the plants yes they got to a couple of the plants but it showed me ways to keep them out of the plants. The best way to keep them oit is to dig potting holes before you place your liner push the liner into the hole that way the roots are only vulnerable from the top. and if you place enough stone 3/4 and larger they won't get to your plants.