A very WARM WELCOME to MASA Junz! Very glad that you found MASA and joined us!
Sounds like you have QUITE a nice system.
GREAT skimmer though!
What lighting do you have?
Also - just a word of caution - the regal tang becomes quite big, and will MOST likely outgrow your tank, at some stage - believe me - they get HUGE - I have one that's +-20cm in size! Luckily I have a 2 metre tank for it to swim in - even MY tank is too small..... issue here is not the size specifically, but more the case that they need/want a LOT of swimming space, and might become frustrated when it get's bigger. Then it will most likely start stressing, and get white-spot (c. irritans/marine ich), which COULD possibly spread to your other fish, and kill them all.....
Sorry to bring the bad news - I know that's NOT what you want to hear.
But, other than that - AWESOME tank!