steve,
that is a great design,... i was thinking about a few mods...
1. i thing that would be too much flow through the fuge.... i would have the left two drains exactly where you have them -- the right 2 i would just add to the return chamber (like a closed loop)
2. the retun i would have come up the middle of the tank and T in the middle. this way it is easier to adjust the flow evenly ...
3. all the way on the right on the T i would have an end ball valve and a union -- this way i can add a flex hose at the end for quick water changes
what do you think?