I know that the vermiculite floats before it becomes water-logged; you
can either let it soak for a while, or put it under some gravel and then
add water slowly.
I hope to start a planted tank with this set-up sometime soon. It will
have a homemade CO2 injector to it (ie some container with yeast and
sugar water).
-- Stephen
stephenbou at aol.com
http://members.aol.com/stephenbou/cichlids.html