Hmm...I grow two D. sanderiana varieties, neither of which is unhealthy. One is the aquatic Lucky Bamboo, the other's in soil, is variegated, and smaller.
JoeC, I'll try to tell you what I know: D. sanderiana is from the Canary Islands and southern Asia, so it probably appreciates warm temperatures, high humidity, and a long photoperiod. Photoperiod is the number of hours per day that a plant recieves light, e.g., a 12 hour photoperiod.
The canes (a clump of nine) are in an undrained container with the water constantly near the pot rim. I do not add fertilizer or Superthrive or anything at all to the water I use, which is distilled because tap water causes an annoying mineral build-up on the pot rim and plant.
Apparently, some people grow the plant in clear glass containers so that you can see the roots. They are wrong--do not do that because algae will often appear in the water, forcing you to clean everything out. Instead use a solid-colored container, preferably not plastic. Also, some people do not fill the container with pebbles, leaving instead a pool of water without a place for sanderiana's roots to take hold. Also, algae is more likely to form in water without pebbles because a lack of pebbles allows the sun to penetrate into the container's water, promoting algae growth.
BTW, I don't use fertilizer on my aquatic sanderiana because 1) it's a hassle 2) the annoying mineral build-up is more severe when you fertilize and 3) the dreaded algae growth is quickened when you fertilize.
My plant (actually, plants) is on a kitchen counter adjacent to a south-facing window shaded by an outdoor roof overhang and a big, annoying Hedera helix. The plant receives filtered sun for most of the day and direct sun for parts of the morning and evening. I know the light is strong because the sanderiana is next to a hydrophytic Spathiphyllum whose vase constantly needs cleaning of the algae (I would instead use a solid-colored container and pebbles as with the sanderiana, but the vase happens to contain Spock, a Betta fish).
The plant is in fairly high humidity, thanks to the transpiration of neighboring plants, occasional misting, the water in its open container, and a nearby ocean.
The plant's health kind of contradicts what I said before about providing high temperatures, etc.: it is thriving despite strong sun and a significant temperature differential from summer to winter (Massachusetts is stranger than it seems).
The plants are around two feet tall, including the leafy offshoots from the canes. About every month, I flush out the container by running it under the faucet, allowing the old, stale water to be flooded away. This, I think, refreshes the plant and discourages algae. The leaves also tend to collect dust, so I occasionally wipe them off with a damp cloth and discourage dust build-up with the aforementioned mistings.
BTW, the most important thing you can do as a plant-grower is buy your plants from a reputable source, such as PFT. I bought mine from a steamy hothouse in a local nursery, but it acclimatized to my conditions quickly.
About hydroponics: hydroponics is when you grow plants in a nutrient solution (i.e, fertilizer-infused water) instead of soil. I don't know if one could consider an aquatic sanderiana to be hydroponically-grown...hydroponic systems tend to aerate water with lots of little bubbles, which promotes plant growth and is not featured in my (and, I think, your) anerobic-watered setup.
Disregard the above paragraph--I rambled and it may not be of interest to you.
Any questions are welcome.
Chris
(Edited by Dionaea Enthusiast at 7:27 am on May 25, 2002)