Too small of a tank for both those Tangs. And 100+ pounds of "aged" live rock (like a year old) is the best way to care for a Mandarin. Those who dont listen and get one anyway usually watch them die. Ofcourse there are exceptions, but please dont listen to the nit-wit at a ***** who will tell you its ok to keep a Mandarin in a small tank with a few pounds of live rock.
The order I would introduce the fish would be something like this....
-2 Perc. Clowns
- either tang, one of the other, but not both.
-copperband Butterfly??? (need To Make Sure This Would Be Okay)
-dwarf Angel