Sump design recommendations for 180 gal.

I agree that it is a good design but I also think it is more complicated then it has to be. I'm also a skimmer, fuge, then return kind of guy

 

I did a ton of research before designing my sump. First this is the orientation of the fuge in the system. The Refugium is a refuge for copepods, amphipods, and other micro fana. If you are pumping 500gph then there is not much of a refuge for these critters. I designed my sump to have the fuge on one side, the skimmer and filters on the other, and the pump in the middle.
I agree that the pump section needs to be smaller. To add to your fuge size. I went with 1 1/4" space between my baffles. I did not put baffles after the fuge because I am only moving about 150gph through it. I did have to put a plastic screen type thing at the top of the water surface to break bubbles before the made it to my light.
I am looking at your return lines and I see that you have one valve, that looks to control water flow with a by pass. I would put the valve inline and control the water flow that way. From what I have read it will not hurt your pump by restricting it this way. Also you can add another valve the way you have that one in the picture to do water changes. I don't know if you can, but I would move the return lines away from the overflows. You will be running a portion of the clean water back through your sump the way you have it designed now, just my opinion.

As for an ATO you can build one yourself if you know how to solder, and it is a fraction of the price. If you need help you can message me and I can help with this. I built one for my tank, and it has an alarm to let me know in case of a failure.

I like your design though.