I think that is an awesome idea. I wish I would have thought of something like that when I set up my tank.

One question though. When you fill the tank up with water and the HC has to convert from emersed to submersed form, won't there be a bunch of "mushy HC" from the emersed parts melting before the new submersed growth fills in?

The HC I got in pots was grown emersed (I believe) and after I planted it, many runners and stems turned to mush and it took a while before I saw new growth.

However, this method sure sounds like it would still work better because the plants are already established with good root and leaf growth. I seems like that would make it a lot hardier and able to make the transition much easier.

Couldn't you do this with most plants that can be grown emersed? Maybe even plant your entire aquarium layout with emersed plants. Grow them in quickly and healthily, get their roots going, then slowly fill the tank up with water.
Could use crypts, HC, rotalas, limnophila, etc.?

Cool idea.

-Mike B-