this is the important bit, trophs as adults should be in a 4 foot minimum & only if you must until a bigger tank is sorted. as long a tank as you can get is best, 5 foot minimum for adults.
dubs can be kept with one other species of trophs & they won't mix, if you mix any other two species they will cross breed. i am most of the way to having a tang community, in my 2.0m tank i have pembas & duboisi, altos & plan to add some leluipi, brichardi or daffodils & will also see how the ocellatus will go in there once they are fully grown.