I'm looking for a plant which grows up the pipe of my undergravel filter (in a 30 l freshwater aquarium), i.e. from ground to the water surface growing precisely around the pipe.
I'm aware that I could use a plant which is so large that it would cover the tube, or that I could put a mat around the tube and let Java ferns grow on it. It's more of a knowledge question.
I'm aware of the fact that the plant would limit the maintainability of the filter installation.
In case you don't know yet, what an undergravel filter is: http://animals.howstuffworks.com/pets/choosing-aquarium-equipment7.htm