Basically, this plant just floats around on the surface. In the wild it would float on the surface because the surface has the most co2. There is one species of Aldrovandra, but it is found in a whole bunch of localities like Japan, Australia, and Europe. The Japan and Australian ones are red and tropical, while the European one is green and temperate. Unfortunately it is endangered in the wild due to habitat destruction, according to what I have read. It doesn't grow any roots and has these cool little bladders? (I don't know the scientific term) for catching miniscule aquatic invertebrates. I just use it as an accent plant and it just looks really prehistoric.
Poor JanS, look at the all the money you save....I wish I lived in a cold area.