I don't know what 'small' lily means, but I assume that they still require a two ft. depth for practical best growing conditions. I doubt that width is a real issue. I also see small preform ponds with lilies even though they are probably less deep so almost anything will probably work.

My containers are only 35 gallons and although I am always removing pads that grow into the spillways, they do bloom and are healthy.

They looked better in a normal pond. I grow only one 'small' lily and it has plenty of space in it's container pond.

Thanks chas and PKponder.
Now all I have to worry about is that it gets enough sun. I might have to cut a few tree branches. I also downsized one of my little above-ground ponds from a 300 gallon tank to a 100 gallon tank. That's why I ordered the pygmy lily. It's hard giving some things up, but the older I get and the more arthritis I get, I've got to come to terms with all the "stuff" I have to do. I hate Fall and having to winterize things and drain several of my stock tanks........but man do I love having those lily blossoms and tree frogs singing in the summer!