One of the problems I see is that having the single overflow in one section or another means that the surface-skimming action of the overflow will only benefit that area. The other two areas are likely to still have crud on the surface, as water flow is impeded by the drilled dividers.
The other problem I see is that there doesn't seem to be a place for any mechanical filtering before the water hits your pump and gets sent back to the fuge. Even small stuff being sucked in can end up tearing a pump up.
What about Keeping both the fuge and seahorse areas 6"x10". Make a shallow overflow box that runs the entire back of the middle section that has teeth on the front, and on the seahorse side. You can put sponge on a tray in the overflow so it has to trickle through it before hitting the bottom and going to your pump. Simply having less holes in the divider between the seahorse side and the central reef section will help keep the higher flow in the center from affecting it much. Then you could use one pump to and t and ball valve to control the flow of all three sections. Or you could use two pumps. You could even divide the overflow as well, (although I'm not sure it would be useful to do so). I'll have to think some more about this. My brain already hurts from work today. Maybe in the morning I'll be thinking clearer.
B
