I like to get one tropical lily each year. The one I got for this season, just last week, has already had all three blooms--blooms to be, actually, since they hadn't fully popped yet--and five giant pads (out of eight) severed. I'm not sure I'm going to have any blooms that make it (although about 7 are coming up from it right now, so some are bound to make it past the koi onslaught). It's what koi do. It's impossible to protect water lilt stalks and pads, but everything else I try to put in a secure place that forces the koi into odd contortions to reach, usually with rocks. Floaters go in a floating mesh ring that I anchor to the bottom. Hardy lilies seem to survive ok; maybe it's just stronger stalks. They're not malicious, just hungry. Always hungry.