Water Lilly problems

Hi everyone!

I'm in the middle of a problem this spring with the water lillies we wintered over from our pond last year. (and what a winter, we've broken every record in the book this year including 170+ consecutive days of snow).

Here's the problem. We repotted the lillies in order to give them a start until the snow is gone. They've already sprouted to a length of 2-3 inches. We followed the advise we picked up from various magazines, and placed them in soil mixed with some bonemeal, and covered this with a thin layer of sand on the top. We then placed the pots into a clean 75 gallon aquarium, (no fish or gravel on bottom) with the water being filtered, and placed a 80watt florescent lamp over the tank giving them about 10+ hours light (on timers).
The problem is that the water has been turning milky white and to put it bluntly, smells like a septic tank. There was a clear film which looked mucoid or jelly like starting to coat the plants and the surface of the water. After a week of this the tank continued to get murkier and darker. The smell was so bad we had to take all the pots out, wash them down, and reclean the tank. 

I've bleached the tank, rinsed, and refilled. We placed the plants back into the tank and hoped we had solved the problem. 

24 hours later (today) the water was getting milky white again and bad smelling. We've drained the water and refilled again (and will do so as often as necessary) until we can find a solution to this. 

I don't think it's the water since I have 2 aquariums running in the house (with fish) and have no problems with them. I even placed one pot into an aquarium (initially before this problem showed itself) and that pot started to make the tank smell. Removing the pot, doing a water exchange returned that aquarium to it's original state (<sigh of relief>).....

Has anyone any idea of what we're up against?!? Any ideas as to how to fight this problem? As things are looking here in Winnipeg, Manitoba, Canada it's still looking like it will be 2-3 weeks until we can get the plants into the pond.