I believe that your problem is that your plant is non-aquatic. Many stores will take common houseplants and submerge them into tanks and sell them as aquatic plants. Usually after a month or 2, they finally just rot in the tank. Next time you want to get a true aquatic plant for your tank, go to [url=http://www.plantgeek.net]Plantgeeks and go to the
plantguide. Choose the link according to how much light you have over your tank, and then get those plants. I think 1 watt per gallon (WPG) is low light, 2 WPG is medium, and 3 WPG is high light.