Opening myself up to the Tang police here but I have: one blue regal/hippo, one powder blue, and one purple tang. All in a 110g tank- 200g water volume. All bought at a very small/young age. They are happy, swim and eat together all the time. They are about four inches now, one day when they get to big, I’ll move them to a bigger home. The purple tang is for sure the most aggressive but not so bad. I however can not add any new live stock to the tank. They try killing anything I've since added to the tank. Also for your info, the powder blue likes to nip at some soft corals and I've had to move one coral to my sump.
Dave
Tang Police: if they get to big or unhappy, I have a mini spear gun.
