The top tank is drilled for drain. I think a hob overflow would not work because of slow movement, bubbles in tube, lose syphon. I feed fuge from sump return with ball valve to adjust flow. You could put a maxi-jet in tank and use vinyl tubing to and from fuge. Hardest part was finding someone to drill glass. If I had to do over I'd drill hole in middle of glass and use corner elbow + pvc straight up with strainer to make it surface skim.
To keep bubble out of return line plumb out of fuge bulkhead into a tee going up higher than water level. Get a cap and drill hole and insert small tubing to quietly vent drain. I think this is a outside duro? Mine isn't vented or surface skimming. Figured it out afterward. Fuge makes huge difference, adds critters, exports nutrients, lowers nitrates and they are cool to watch. Mine completly shut off my remora skimmer. It produced nothing for weeks. I hope that helps.