[ReefSparky]

Wow, we almost do have the same fuge! Both homemade, too! That's good stuff. I showed my wife your fuge and said, "See honey, I'm not the only one doing this stuff." LOL . . .And he's a guitarist too!

The only issue I see with a stacked system as you state (fuge above the sump) is control over water when pwr goes out. However, so long as the fuge drains from the top (ie, overflow box or U tube) you could have some control over this, I suppose.

My system currently does exactly what it should when the power goes out. The wet/dry fills to within 8" of its top, and the fuge stops at about 2" shy of the top. When the pwr comes back on, everything levels itself out.

Sleeping well at night, priceless.

What I've seen others do, which I like, is have a sump with the return in the center, and fed by a T'd overflow box from either side. This way, a 1200gph overflow box (double U tubes) can be T'd into 2 diameters--the larger diameter feeding one side of the sump, the "slower" diameter feeding the other side (fuge side). This is simpler, and IME, simpler is better.