plant filtration

[Frauley/Elson <fraulels@minet.ca>]

Hi all,
The idea of experimenting with plant-root filtration has appealed to me
for some time. Can anyone tell me how the plant is held on top of the
tank? By this, I mean what rooting medium, if any, is used between the
stalk of the plant and the roots in the aquarium water?
Gary

PS -technically, this is maybe off-topic, but anything that improves
apisto water quality is in range to me...