How deep it goes depends on the type lily it is....I would definately put it in
a larger pot.....Get it AWAY from the waterfall....lilies like still water.
Depending on the kind of lily ...a medium sized one is more than enough for a
400 gallon pond, since they need to be away from the waterfall. Jerri

http://www.fringeweb.com/Ponds/JerrisPond