This winter has been really crappy! On the coldest day this year, we actually had to heat a pot and set it on the surface to open a hole in the ice of the pond for out-gassing. This is with 3 airstones and a de-icer running as well! Bleh!
I probably wouldn't have any issues with the lotus overunning my pond because my koi are such little pigs. They eat anything slower than them.