Tangs generally get along fine together, given enough space, provided you follow a couple simple rules. When mixing Tangs of a different genus together, you are typically ok, provided they are not the same color. The Blue Hippo Tang is a Paracanthurus; The Yellow Tang
is a Zebrasoma. No problems, as a rule. You should be ok.
If you decide to mix multiple Tangs of the same genus, they should be added at the same time. For example, a Yellow Tang
, Sailfin Tang
, and Purple Tang
should work out ok if added at the same time and given enough space. I would suggest a minimum of 50 gallons per Tang, if mixing the same genus. In my 180 I plan to have a number of Tangs, and will mix them liberally following these rules.
By the way, you should treat the Chenochaetus genus as a Zebrasoma, for the sake of these rules.