It sounds like it would probably work, but it is not ideal. A soft silty bottom is best, but I have gotten a similar species to grow in a solid clay bottom before.

Another idea is to pot them...when we pot them for water gardens we use a mix of ~ 75% heavy garden loam & ~ 25% sand topped with gravel to keep the Koi out in a six gallon container (squat and wide is best...we use a 16" x 7" pot). You could cut some holes in the side of a container to let the roots spread out.

Mike Robinson
Keystone Hatcheries