Thanks for your advice;
Limnophile

"Dr Engelbert Buxbaum" wrote in message
...
Chris Oinonen Ehren wrote:

Note that in a closed system plants can grow only as far as available
carbon (and other nutrients) allows. This is completly different from
the standard aquarium tank, where food and CO2 from the air would indeed
allow mass propagation.

The question really is which plants and animals can live together in
that little biotope, and it might help to have several species to begin
with. Some will wither, others will grow.

Appart from duck weed, there are some other surface-swimming plants with
nice "roots", like _Riccia fluitans_.