I don't have a cube, and don't really know what the exact setup is, although I've seen the back sides of these units.....just a thought, is there anyway for you to gravity feed from the over flow compartment down to a 10g sump? That way you could use almost any skimmer (within reason). You'll just need to figure out the overflow rate and the return rate, subject to head height and return pump. Just a thought.......