That looks great!! My H. polysperma grows that fast also. Also my Cabombas are so tall they are starting to block some light out. I guess I now realize why H. polysperma is considered a noxious weed!!
I see you use the Hagen ladder, what is your co2 ppm?
ps...if anyone else reads this, can you suggest a way to trim my Cabomba? I really like the way the tops of the plants taper to the water and "fray" out, and it would be obvious that if they were trimmed, they would look sort of "chopped" off on top?