HTH wrote:

I have been looking for something to pot plants in (esp water lilies)
that will not (with koi help) dump dirt into the water.

Clay is the best and the best source of clay is Walmart's cheapest kitty
litter at a couple dollars for a huge bag. It is pure clay with no scent
or anything else. First I put a layer of 3/4 inch river rock on the
bottom, then the lily tuber covered with the kitty litter, and then I
cover the kitty litter and lily tuber with 3/4 inch river rock. You can
add pressed sphaghnum moss "paper" as a filter to help keep the clay in
pond baskets. I personally don't bother and haven't had any problems.

--
Pardon my spam deterrent; send email to
http://home.earthlink.net/~rhodyman