What is your water temperature in your pond?

How deep do you have the plant??

The soil surface is 3-4" below the water surface. I don't know the water temperature. My pond is four feet deep and is in full sun. The high temperature is around 92F and low around 70F. A pond store representative thought my pH is too high. It is 7.8 or so. She also thought the plant is getting too much sun and not enough fertilizer.

What kind of soil did you use? Did you use clay from the yard or some sort of bagged soil? Gravel? Sand?