http://www.molbaks.com/infopages/dieffenbachia.pdf

"Dumb Cane? Dieffenbachia species...

WATER: Dieffenbachias are especially susceptible to root and stem rot. Allow your Dieffenbachia to dry thoroughly in order to avoid this problem, especially during the winter months when the plant receives less sunlight. Stem rot is first evident by a very unpleasant odor; if allowed to progress, the rotting base of the stem breaks off.

Check the soil moisture before watering your plant. You will find that the time between watering varies with the season. Plants adjust their water use based on external factors of sunlight, temperature and humidity. To check, insert your finger into the soil to a depth of at least 2 to 3 inches. If the soil feels wet, don't water. If it feels dry, it is time to water,"

Dumb cane will also shed extra moisture through the leaves. That can be in part a noxious chemical.

So I wouldn't try it because it will probably rot in water. Secretions from the leaves are not good for family and pets and I wonder about whether they would be safe for fish.
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Googling for [dumb cane in water] lead me to another plant called water bamboo. This was a Zizania species, which turns out to be hygrophilous (water loving) rice. Turns out it is a kind of rice. People raise it for the edible stalk. Rice plants are grasses, but unlike most grasses they do well in water. In time the grasses usually rot.

However maybe the use of the terms hygrophyte (a plant with leaves partly or while submerged in water) or hygrophilous plants are useful search terms. One pond plant group whose tubers are often out in those inert black plastic pots are cannas. I have spent years, here and "back when" at my folks' place, digging up and hosing clean too many of those tubers. Then we got to plant them on 70-foot rows every spring. (Now I have a patch planted in a sheltered SE corner of the house. We just put two feet of leaves over them and for about 8-9 years most have survived.)

I actually bought a couple of unusually colored cannas last year, for the container gardens, while at a pond trade show.. The raccoons trashed them. Sigh! A couple small ones germinated in one of the trashed pots and from a pile of stalks from the terrestrial cannas. Tried to keep a couple of the really small ones indoors last winter and they didn't work out. They basically kept drying out in small jars of water.

If one has access to rainwater or RO water, topping off pots of water plants can be as important as replacing evaporation in fish tanks. Winter months can be tough on both.

Two ideas have spun off of that canna experience. There are a couple of small cannas outside. One will be replanted in a small black plastic put. The cheap clay used as kitty litter (non-scented, non-everything) will be used as potting medium, maybe over a little black soil. It will go in one of those well lit tanks with a little window light.

If cannas are germinating in the stalk pile, some seeds must be over-wintering. Soooo... why not pick a few seeds, store them in a labeled pill bottle and germinate a few of them in a (covered?) plastic shoe box. At a certain size put them in one of those pots of kitty litter and plunk them in a tank where the leaves can extend out above the water.

It is hard to over-winter water hyacinth. They need a lot of light (growing weird stalks trying to reach light if they do not get enough) and they are heavy feeders. I suppose putting them in tanks used to grow out a good sized crowd of youngsters (always eating, always pooping) might take care of the nutrient factor.

The smaller plants from outside may actually adjust more smoothly to life indoors. Many times they were somewhat in the shade and not so dependent upon bright sunlight.

A tank heavily covered with Salvinia natans, which has reproduced and grown like crazy in the containers outside, crashed. At least the Fundulopanchax walkeri died. I'm wondering if the plants sucked critical elements out of the water. The problem wasn't nitrogen poisoning, unless the leaf litter was too great and decaying.

The lessons? Don't over plant floating plants, which have been outside. And change the water, change the water, change the water... Plants respond as well to water changes as do the fish.

Ah! And please don't dump Salvinia or any of these others in local lakes, ponds or streams. One never knows when they might become pesky invasives.

Bamboo in yards, especially if it is not a clumping form, tends to spread out more one may want. Isn't that the way with some plants, whether in the garden, yard or aquarium, - they either don't grow well or they are so robust they become invasive! I'd just ask him for clump next spring. Lots of info on that sort of things is available at http://www.americanbamboo.org/   I'd also leave the regular bamboo out of aquariums though. :)

New Guppy Momma, I really do appreciate your expanded inquiry into what plants are water-tolerant. Especially with the availability of brighter and more energy efficient lighting available these days, some things are within the reach of aquarists, which would not have been too many years ago. And that makes the hobby even more interesting.

Those hoods with the dinky 15-watt bulbs though, are not going to be useful for more than the low light plants. Googling stronger aquarium lighting, visiting sites like http://www.aquatic-gardeners.org and searching their forum or following their links would help. (They have some useful commercial links too.) Don't necessarily stop with http://www.geocities.com/cagagroup/ but look for more ways to retrofit aquarium hoods.

Also look for local groups. Quite a few urban areas have them these days. Check out their home sites and forums if they have one. Also search the Aquatic Plants Mailing list at http://fins.actwin.com/