I actually have a really big varigated potho's growing and hanging over the side of my 220g. I started them with some cuttings from one of my house plants and loosely tied the stems together, hung part of the stem in the water (with the leaves removed off the stems that were in the water), and drapped the rest of the stem with the leaves over the side and up against the hood. After about 4 months they have become a beautiful hanging plant, which is actively growing, with its roots in the water (using nutrients). The tetras and oto's like to hang around the roots and when the roots get too close to the substrate I just cut them shorter with sissors. It give a nice touch to the top and side of the tank, there is also alittle bit I let drape onto the front corner. I've seen alot of planted HOB filters, its becoming very popular but one thing I always noticed was they had them where they go some kind of light, either artifical or indirect from a window. They are pretty neat. I'll see if I can find the one and post a link to show you.