Sump Plan - Good or Bad?

For my 75g reef tank, I have enough space for a 55g sump or a 29g sump/fuge with a separate 10g tank for the return section. I have all 3 tanks, but the 29g w/ 10g would be easier to do(need to reseal the 55g). SO I drew this in Google Sketchp to make sure it would work. I have heard of this being done before(2 tanks for a sump), but what is stopping the 10g from overflowing when the return pump is turned of??? .

Here is the sump in the bottom of the tank stand...I plan to use a 29g for the skimmer/fuge section. This will be drilled and plumbed down to a 10g which will be used for the return section. The first(from top) red and green lines are the two OF lines. The continued red lines show the direction of flow. Yellow is the return line.


Back of stand...


I know you are supposed to leave enough room for the extra water(above OF box/in plumbing lines) to be in the tank when the pump is off, but then for a 2-tank sump wouldn't water go into the 10g? Would this work?

 

Bump..I guess I am alright...I just need to make that, extra room that's needed, in the return tank, rather than in the skimmer/fuge tank...

 

I would do the fuge in the 10 and have it empty into the 29's return section. You want flow to go through the fuge slowly so the algae can remove more nitrate and phosphate.

 

I will have 2 overflow boxes(one in each back corner). Both, split...one part to the fuge, one part to the skimmer. I will have a shut-off on each OF line, as well as a ball valve to adjust the flow going to the fuge(22" X 9" X 16") in the 29.

I can't easily have the 10 go into the 29, as I only have 22" of height(floor of tank stand to top-inside of it). The 29g is already 18".