i think u need to supplement yr lightings with T5...dun think is enough with 2 230W maxspect...in terms of the length to cover 6ft end-to-end.
Return power of 16,000 l/hr, sounds scary...
Sump tank thickness, i would suggest 10mm - 12mm instead of 8mm..considering the amt of water and the vibrations caused by the return pump...to be on a safe side.