Goldfish do eat many things but they don’t really eat pond plants and water lilies like koi fish do. Goldfish may pick at pond plants and water lilies a little but they will not disturb them like koi.
You see koi fish are scavengers and they have barbels also known as whiskers under their mouth in which they used to search for food. It’s in the search for food that koi fish disturb plants in ponds. They may pick and eat water plants but not so much.
I know goldfish don’t grow nearly as big as koi fish do and this may be a factor. I know I’ve had many koi and goldfish and koi don’t really bother my water lilies at all. The worst they’ve done is uproot a hardy water lily in the past but that’s my fault as I didn’t put large rocks around it to prevent it from happening. As far as goldfish are concerned you don’t have to worry about them eating your pond plants and water lilies. Keep your goldfish well fed and you’ll have no worries of them eating your water plants.