I work at a LFS and we carry saltwater fish also and this has also got to me. I know that two tangs that look alike should not be in the same tank, but have always kept 2+ yellow tangs in our tanks. Of course we are the store but still, they have only faught one time and that was when someone that didn't know anything about them put 3(!!) in like a 20Gallon tank. That was bad, had to put them all on seperate tanks.