thanks steve, i see what you mean. essentially the spray bar and om 4-way are t'd off from the pump so the spray bar is always going and the outlet's from the om are alternating/switching.
not really an option to drill since the tank is already in place and functional. unfortunately the bottom holes are 3/4" and combining two of them to give 1.5" to the pump is my only option. however at 13,500+ litres per hour @ 0 ft head even a couple thousand lt/hr less is not really a concern
dont forget that the tank is only 5 foot and it will ALSO have streams. the closed loops are purely to shift water and hit any dead spots (under the reef rack). each outlet back into the tank (near the top) are drilled 3/4" as well. each outlet is also running a rotating flow nozzle which disperses the water around the tank quite well. not sure on how these will go at such a large increase in flow rate - not a concern if they dont work though, millions of ideas to play with! the streams will sit at either end near the front pointing across and slightly towards the back. remember this is only a 5 foot tank - i dont particularly want my fish to go surfing :lol:
here's a pic of the back of the tank again, holes drilled near the top:
rotating flow nozzle shown here (old photo, oct 2004):