I've had the sump in my tank going for several weeks and have been battling microbubbles in the display. I have a 3 baffle bubbletrap after my return/skimmer section, this drains into the return section where the water level is about 1/2" lower that the skimmer section. I also have a refugium on the opposite end of my sump with a single baffle separating it from the return pump. The water falls about 6 1/5 inched into the return section. Water flow through the refugium is pretty slow. My return pump is a Jebao DCP-4000. I have a soft line runnimg from the pump up to a pvc "T" which feeds my UV sterilizer and the return lines. The return is a straight run of 3/4" pvc up the back of the tank with a 90 degree and 45 degree elbow terminating in a "T". On either side of the "T" is loc-line. I've tried slowing down the return pump speed from 100% to 60% but have seen no noticeable difference in microbubble quantity.