Final Fish Selection

[dkmcelroy]

I have 11 fish and would like your recommendations for the 12th in my 15 gallon display... current inventory is:

Regal Angel
Blue Hippo Tang
Yellow Tang
Sailfin Tang
Foxface
Starry Blenny
Firefish
Purple Dottyback
Black Ice Clown
2 Pajama Cardinals

I was thinking a purple tang... what would you add to this group in a 150 gallon display?