This is a new tank...not a new skimmer, pump, GFO or Carbon filter. Used water from old tank and new water.....old and new rocks.....new living sand. I would get these same bubbles everytime I did a wc in the old 75 and would just put a sock over the two outlets. I don't know what to try since this is a drilled tank and I used to have the water box. Will post pictures as soon as someone gives me directions on how to do that. LilRobbs MM LED's are beautiful but having a custom made canopy to hide the fact that they are suspended ..this is in our breakfast room and isn't eye appealing over waffles and coffee. I know that there is the old NEW Skimmer syndrome, but as I said nothing is new but the tank, sand and 30 lb. pukani rock. The bubbles are coming out of the 4 returns in the display tank. Any info will help. Thanks, Bubba