I've got a yellow, purple, hippo, and powder blue tang all in an 80g tank. At first, when each one of them was introduced, they were outcasted by the others for a day or two. Now, they all live in harmony and actually pal-o-round together. I just made sure each has it's own hiding place in the live rock and that they were all about the same size. I have never had a problem with them getting along. Every once in awhile one will get testy with another if the other is in it's special hiding place.