Is it already plumbed? Just wondering, because if you could plumb it from the bottom it would allow the water to run over more surface area in the filter media. Also, if you add another corse of block to the front of the box it will make a taller first "falls" down the slope, making it louder and more areation. It looks like it will be more of a stream than waterfall into the pond, quite randy looking, and well thought out.