I have a H&S A200-2-1260 external skimmer placed inside a 130 gallon sump. It was part of the package. Upon startup with 100% new water it shot foam within minutes of startup through the holes in the lid and running over the sides. Completely out of control! Prior to my purchase I had seen this up and running externally. Now inside of the sump I stared at it long enough to appreciate its simplicity in function. Immediately put my fingers over the air intakes and bubbles stopped, began tweeking those. Next the outlet/discharge was reduced from the metric piping to a 1-1/4” ID, dismantle, tear apart, removing the restrictions on the outlet lowered the water level in the chamber...reconfigure discharge to reduce backpressure and eliminate noise (including vibration dampening pads) and Bobs your uncle! The single largest factor (besides water quality) is the water level in the sump, mine runs sweet at approximately level with the venturi. 2” pvc or abs fittings fit over the outside diameter of the factory tee. A cap drilled with a ¼” hole in it then placed over the top of the tee, I seldom fuss with the wedge pipe, unless I want to wet skim, combine the drilled cap with a long radius 90 over the branch of the tee I’ve extended this below the water line…only here the pumps. One day a Eheim sounded as though it would grind to a halt and it did the pinwheel impeller broke into pieces. Replaced with one from reef dynamics.(thanks to all who post here as many a google search has led me to RC). All is well but I am fascinated with using the overflow return to eliminate a pump feeding the skimmer and may extend that further trying to capture as much energy as possible to an ATS…the free gravity feed is taunting me, asking to be tapped.