I found them to be pretty easy. I planted mine in play sand in oil-change drain pans. From Spring to Fall they receive 1 or 2 lily fertilizer tabs, per month, pushed in the sand about 3" from the rhizome. I only stock hardy (term for cold-hardy) species so I don't have to remove and wet store the rhizomes indoors during the winter.
The pond holds flag fish, trapdoor snails, and sailfin mollies so the plants don't become overwhelmed with hair algae. My 'eye-catchers' are the Wakin goldfish and these don't damage the water lilies. Gammarus shrimp keep the bottom clear of organics, as well as the snails.