This thing should take off like a chia pet in a couple of weeks. The Riccia should grow through the grid in search of light, forming a nice carpet. When the Riccia grows out of control you can remove the whole grid and trim it outside the tank, no mess inside the tank. Brilliant, to bad I didn't think of it! I'm trying a pretty big one, the examples I've seen were much smaller. My only concern is the Riccia in the lower part of the grid won't get enough light and die off. I could always flip the grid around if that's the case. I got the grids in the craft section of Walmart, only place I could find them. They come in large and small sheets, cheap to. 2 large and 2 small cost 6 bucks.