"Haywire" wrote in message .cable.rogers.com...
Someone in my office suggested filling a tube with the substrate you want
and somehow blocking it from spilling out, placing the outlet at the level
you want in the existing gravel and then somehow opening the bottom of the
tube. Now I've used a similar technique when using cement grouts in wall
cavities but maybe the same could be done with a funnel and hose, you'd
probably spill a bunch into the water too

Diana Walstad suggest wrapping up paper parcels of soil and pushing
them into the gravel. I've not tried retro-fitting soil, but I'd
recommend it as a growing substrate:

http://mike-edwardes.members.beeb.net/plant/lotech.html

Mike.
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Mike Edwardes Tropicals
http://mike-edwardes.members.beeb.net