Phyllis and Jim wrote, On 08/06/2008 13:58:
You have good answers.

Our main pond is cement. No root penetration! Plants float, grwo
wild on the bottom or are in pots. Fish waste provides nutrients.

You all seem to be forgetting that a plant gains it's primary source of
nutrition by fixing co2 into sugars using energy from the sun. The
sugars are used as building blocks to grow, and fuel for other
processes. It's roots take up water and molecules such as nitrates,
phosphates and metals to help build proteins for specific processes
(such as photosynthesis). Luckily for us, fish crap out those kind of
goodies continuously.
People often make this same mistake about carnivorous plants, completely
forgetting that they are green and photosynthesise like any other plant
to generate their own food. In their case, insects provide the molecules
that don't exist naturally in their soils.

--
DavidM
www.djmorgan.org.uk