Nice big " HUGE" tank,wish you all the best setting it up and that rock looks great,that's one thing I wish I did differently instead of dry rock and wish I could have a huge tank but sadly on 3rd floor would be huge task just getting it In ha ha.
Only experience plumbing my basic 80g up but interesting how most in this thread advising use gate valves rather than ball valves as in plumbing its other way around and that gate valves fail more often so always used ball valves where possible, ( not saying the people in this thread are wrong just what I got taught at college and years I worked as a plumber is all) little tip on gate valves never completely open all the way,just open fully then close just a touch and if ever get stuck then you can try open it both ways,this helps alot .
Anyway good luck you got a beauty of a tank,is this your first saltwater tank ? If so you more than took the advice of bigger tanks give more stability ha ha ^_^