Many local reefers I know have both PT & YT together in the same tank (100g & up). I have 3 YTs together & they get along 95% of the time & spar occasionally without actually doing any damage whatsoever. Maybe suggest getting the 2nd fish a little bigger since the 1st would have the home field advantage. To get my YTs together, I placed later fish into my eggcrate isolation chamber & sunk it in my display tank. That way the fishes get to see & smell each other for 5-7 days before release, by which time the aggression levels are way down. Still, it will depend on the individual fish's temperament. Some fish will just never get along so have another tank ready or someone willing to adopt. (I do
)
JME
Anthony