I like this. I like it a lot! The million dollar question though is how big a pump should I go for here?I'd do something like this:
mainly because I could carve a sick low profile overflow and overflow box for it.
I'd actually do 3/4" plumbing throughout just to simplify, because you have so many holes, and because the stop valves are only $3....
I'd run UV and reactors through the closed loop... make that a gigantic pump...