I run the Jebo 520. It's the first skimmer that I've ever run and I'm not sure how well it works compared to the other, more popular brands, but my tank parms are in-line and my critters are happy.
The skimmer sits on a stand, outside my sump. I adapted the metric pvc to american std sizes with flex-tube and clamps. I originally had a 1" ball valve on the output side to adjust the water level in the skimmer but after it broke in, I found that I did not need this and I could make the necessary adjustments via the air-valve. I find that the venturi seems to clog easily. So I stop it for about 1 min and restart it once every day or so as I'm doing my daily tank maintenance.
I'm sure that there are better skimmers on the market but this one met my needs for about $100, including the pump.
Hope this helps!