Thanks everyone, so I have started work and will be building the refugium in the next week. I'm figuring out the layout of plumbing and has one additional question. I plan to have the refugium empty by gravity into the return section. The sump I'm using already has a hole drilled in it that I plugged since I'm using a submersible pump. Do you see any problems with having the refugium overflow into the return center through the bulkhead. It is under water within the return section. I would plumb the refugium into it and remove the cap.