I'd only do 1 pair of clowns and two of the tangs. Clowns are damsels don't forget and can get territorial, expecially when breeding. I see I'm too late on that and you've already done both. Good luck. 3 tangs and an angel require a lot swimming space. Again, territory start to matter with 4 swimmers like that.
Add the yellow tang last and he's gotta be bigger than the first. Yellow can be real mean in my (and others) experience.
A sand sifting bogy can be a pain and a big help. The 2 spots will die and won't last. The larger ones will cover rock and coral near the bottom and drive you crazy IMO
Get nassarius snails for your sand, but a good vacuuming when doing PWCs is best for the sand IME.
Clowns and others need vegetable and meat. Tangs, mostly veggies are better, but will eat meat.