When you are planting anything in a container in a pond keep in mind
that some day you will have to drag it out again. Make sure with soil
and water and mature plant you will be able to lift the full container
without making an absolute mess in the water or giving yourself a
hernia. In the beginning I used larger, heavier containers than I do
now. Now I use the absolutely smallest one that will allow the plant
to grow well. And if possible I use a container made from plastic
with a minimum of soil in the bottom. I also stack rocks on the soil
surface to prevent fish from digging around, but I carefully remove
these before trying to hoist the thing out of the pond for
transplanting, dividing, etc. Keep it as light as you can. Its easier
to put a plant into the pond than it is to drag it out. You will be
thankful later.

Lalu