Plant tissue does not usually become ammonia, animale tissue does. Rotting plant tissue is more likely to cause a rise in the Nitrates.
The reason I asked you to go to the
http://www.plantgeek.net site is that they list a great many plants that are similar to the one you have and they are all unde "stem Plants" if you could identify it for us exactly if really would be easier to help you with it.
The one thing I can tell you is that plants with a color to them other than plain green do take more light as they need more than the regular amont to keep their color.
Rose
