Earlier this summer I took the trimmings of rotala from my 55g indoor aquarium and placed them in my outdoor pond. They grew beautifully in the the upper chamber of my waterfalls above the lava rocks. The rotala covered all the plastic borders of this upper chamber thus creating the most realistic/natural affect. The rotala is actually creeping over the adjacent ground...it is so lush(now one can see these are truly marginal plants). I anticipate it wiil die soon with the onset of cooler weather here in Ohio. I'm curious if any other pond keepers have experimented with tropical aquatic plants in their outdoor koi ponds?