plumbing help !! PLEASE

[BMW Rider]

Basically your plumbing layout looks reasonable and should work. I would use nothing smaller than 1" pipe for 1200 gph of flow. You will have some head loss, so if 1200 gph is you desired flow, you will need to oversize the pump a bit to acheive that due to the head losses. A Mag 18 would probably give you what you want. I too would tee the refugium line off just after the pump, but its mostly a case of where it will best fit. I would also rather have two pumps in the system. One for return from the sump, and a second on a closed loop just for circulation. That lets you seperate the returns between the two pumps, making it easier to balance the flow from each one. You will not need as large a pump for the return pump in this case, and you will probably be able to get even more flow with two pumps than you could with one. Another bonus is it provides you with a backup system in case one quits.