Hi Rah,
I recommend pots without holes for plants. A couple layers of newspaper can seal the holes to keep the dirt in the pot with holes.
Plastic kitty litter tubs will do.
5 gallon pots work best for lilies. Wider is better than taller . Hardy lilies tend to grow more laterally than tropicals a need bigger pots.
I use back yard dirt(sand) in my pots.
DO NOT USE POTTING SOIL it is made from wood which floats and won't stay in the pot.
I put 2" washed sand as the top layer of the pot to keep the water clear.
I fertilize when the water temp is 70+
I use agsafe. Pond pearls when I repot and 5 tabs per pot every month.
Tabs I push in with my finger as deep as my finer is long.
When I can't push through the lily roots, I repot.
Gardenlink.com has good prices on the AgSafe if you order large quantities.
I also use Jobes tomato spikes. I can't guarantee jobes are fish safe.
I have used the jobes in fifty gallon ceramic pots that have gambusia and Sailfin Millie's and the fish do fine.
Some of the fish or their descendants have been in the pots for three years.
Three spikes in a five gallon pot every month should do fine.
Around here all the pet stores carry some brand of lily tabs similar to the AgSafe for around $18 for 60 tabs
Jobes is $4 for 50 spikes.
Have fun.