over flowbox help

the tube that keeps the siphon going, one side is longer then the other does the longer side of the tube go in the black acrylic box inside the tank or to the outside box that drains down into the refuge/sump and should the black accrylic box be set low as possible or high or imbetween?

 

in mine the long end of the u tube gos in the outside box and the black box in the tank is adjusted to control the water level in the tank.

 

When I had a OFB, the U tube, the end of the tubes were the same lenth. But if I had to guess, I would say that the longer end goes on the outside(sump). As for the height, that depends on where you want the water level to be at. Luna