It’s generally not a good idea to house two surgeonfish (or tangs) of the same genus in the same aquarium, especially if the aquarium is less than adequate in size. Typically, tangs are quite aggressive toward each other anyways, and this territoriality is often exacerbated when two individuals are either the same shape or of similar colors. For this reason, it’s wise to pick and choose tangs from multiple genera if housing several in one aquarium. This may not stop aggression completely, but it will certainly be the best way to prevent the worst of it. This same ideology can be applied to other types of fish as well…such as angelfish, basslets, and so on.