Look, the important thing to remember is there are no absolutes -well, maybe a few - in keeping marine aquaria. To the topic at hand, trying to keep purple and yellow tangs together often works, but sometimes it doesn't. Depends on controllable things like tank size, other tankmates, how much they are fed, etc. as well as on uncontrollable things like individual temperament.
I currently have a purple, yellow and sailfin in a 265. They have all been together for almost four months. The sailfin gets left alone, but the yellow and purple are always going at it. Not to the point where I worry for the safety of either, but the purple regularly has chunks missing from its fins.
I currently have a purple, yellow and sailfin in a 265. They have all been together for almost four months. The sailfin gets left alone, but the yellow and purple are always going at it. Not to the point where I worry for the safety of either, but the purple regularly has chunks missing from its fins.