A recent article discuss some of these aspects. "L. Adamec (1995) Ecological
requirements and recent European distribution of the aquatic carnivorous
plant _Aldrovanda vesiculosa_. Folia Geobotanica et Phytotaxonomica 30:
53-61". As far as I recall (I have only read the abstract), this species
grows in waters with a high CO2 concentration. To imitate such growing
conditions, certainly is worth the effort (own experience with plain aquatic
plants)and this should probably apply to the more difficult-to-grow aquatic
_Utricularia_ and _Aldrovanda_as well (provided your plants receive adequate
light). To increase the CO2 concentration in small volumes of water is
rather easy. One simple and cheap method is the yeast method where
fermentation of sugar in solution gives CO2 which is directed into the water
of your plants. Those interested can check out the Aquatic plant mailing
list, FINS (http://www.actwin.com/fish/), The Krib
(http://www.cco.caltech.edu/~aquaria/Krib/)or The Aquatic Gardeners Assoc
homepage (http://blake.oit.unc.edu/~fish/aga/)where topics concerning the
culture of aquatic plants are discussed. (Just mail me for more information).
Hans Martin Hanslin