I think I see now... are you going to have your overflow go half into the refuge half into the skimmer section, or any amount in between and then let it do its thing, once it gets too full it will drain out of plumbing and into the bottom section, I would have that plumbing go all the way down to the bottom to where the water wont have a cascading waterfall effect (for noise reasons, and excess water agitation) maybe get your pump figured out and make a few more bubble traps along the bottom? throw in a few more baffles before the pump and you shouldnt have a single bubble in your tank... I mean you have room judging by those dimensions. if its really 17 gallons? is 1'x1'x1' really a 12 gallon area for the skimmer and fuge areas? seems kinda small, mine is like 2 feet long and a foot tall and its only 10 gallons filled to the top...