Give it a try. I got mine off of ebay(half the price of the lfs). I place my diffuser at the bottom of the tank, on the right side pane, midway between front and back(see the debate on placement of diffusers, as apparently this is a giant pissing contest. This works for ME). I have the koralia on the back glass pointed forwared and slightly down. It is at the top of the glass. None of the co2 bubbles make it to the surface.
They are pushed down the front glass, and around and eventually some make it to the surface, but not much at all. My drop checker stays green all day long(and I have 2 hob filters that I'm fighting against).
If it turns out to not be enough flow(and it should be) then you could add another nano to the other side of the tank. The only thing that I don't like is my sunset leaves end up covering the pump every time I move plants around.