How does it propegate? would it be a good plant filter for a sump style
filter? Or would it be hard to keep out of the main tank? I would think
simple mechanical filtration would be able to keep it in place.

Unrelated question... does anyone ever light their tanks from the side?
Does the glass make a significant effect on the amount of light that
passes through? I ask because I have an all plant aquarium for growing
out plants on a shelf that hardly has enough room for the hood. It
would be so much easier to put the light fixture behind the tank for
easy access to the surface.