Pretty simple. I started one, but it made a huge mess and I never went back to address it when other things popped up.
A pump with some PVC
in the shape of an "L" going up and over with a slit down the middle for some or the plastic grating...name is escaping me but people use it for needlepoint like stuff. As always, a ball valve on it to adjust the flow. Of course, don't cap the end of the PVC
Now, this design doesn't like to stand up on it's own. I suggest another piece of PVC
to attach to the capped end and hold it all up. I've seen designs where they have made a giant "U" to hold everything up, but I personally wouldn't want there to be any buildup in the arm end, as there wouldn't be very much flow going through that at all. Best to avoid it IMO