I didn't read anything about what kind of tang you have in there already .
But other then a bristle tooth , or a small species of tang it should have been added last just cause they are known to be very aggressive towards new additions .
The blue ring will grow big too fast .
Mandarins are very hard to keep , they are very picky eaters , they mainly feed off of pods
, something that takes a system many months to a year to establish a healthy population .
A Foxface is a nice fish , I have a one spot rabbit fish .
It is venomous so be careful handling it , probably the heartiest fish .
I have read about complete tank crashes leaving the Foxface as the only survivor .
What's your system ?
Lights , filtration , skimmer ?
What's your future plan ?
Maybe that will help you towards your end goal of what you want