Doesn't need to repotted unless it is near or has hit the edge of the pot.

The lilies I have in the lily pond are in weed-fabric-lined rectanglar
baskets, sandy soil with strips of weed-fabric on top of that with a few
rocks to hold down the weed-fabric. In the koi ponds it's the same, only I
have a lot of rocks on top to keep the koi out of the sandy soil. I repot
if the main part of the plant has made it over half way across the pot in
one season, or I at least prune off babies that will hit the side of the
pot real soon.

~ jan (Do you know where your water quality is?)